Patent Publication Number: US-8987570-B2

Title: Keyboard device for electronic musical instrument

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard device for an electronic musical instrument such as an electronic organ, an electronic piano, and the like. 
     2. Description of the Related Art 
     There has conventionally been known a keyboard device for an electronic musical instrument described in Japanese Patent No. 3074794. In this keyboard device described above, a key touch feeling (reaction force against a key depression/release operation) on a front end of a key, to which a higher pitch is assigned, is set lighter in order to generate a key touch feeling similar to a key touch feeling of an acoustic piano. This keyboard device has plural hammers, each of which rocks through an engagement with the corresponding key so as to apply reaction force against the depression/release operation of the corresponding key. The plural hammers are common components. In this keyboard device, the length from the pivot point of the key, formed on a back end, to the front end of the key becomes gradually longer toward the keys on the high-pitched side from the keys on the low-pitched side. In addition, the position of the pivot point of each hammer is gradually shifted backward from the low-pitched side toward the high-pitched side, by which the distance from the pivot point of the key to the engagement position between the hammer and the key is set to be the same for all keys. 
     The conventional keyboard device described above has an upper-limit stopper for restricting the upward displacement of the key, the upper-limit stopper being provided posterior to the front end of the key (the end close to a performer). An engagement portion extending downward from the lower surface of the key is brought into contact with the upper-limit stopper. The key tilts such that the back end of the key becomes lower than the front end of the key during the key release state. Therefore, if the length of the engagement portion in the vertical direction is the same for plural keys, the height of the portion, which is just above the contact point of the upper-limit stopper on the top surface of each of the plural keys, becomes the same during the key release state. The shorter the key is, the larger the tilt angle of the key during the key release state becomes. Therefore, the position of the front end of the shorter key out of the plural keys is higher. As described above, the appearance is not considered in the conventional keyboard device. 
     The conventional keyboard device described above also has a lower-limit stopper for restricting the downward displacement of the key, the lower-limit stopper being provided posterior to the front end of the key. The lower surface of the engagement portion is brought into contact with the lower-limit stopper. Therefore, the rocking range of the front end of the shorter key, out of the plural keys, is larger. A hammer is engaged with the corresponding key at a portion posterior to the engagement portion. The pivot point of the hammer of the shorter key is closer to the engagement portion. Therefore, the contact position of the hammer with the shorter key in the key release state is higher. Accordingly, the rocking range of the hammer, engaged with the shorter key, with the key is larger. In the conventional keyboard device described above, the hammer can rock apart from the hammer. However, as described above, since the rocking range of the hammer with the rocking movement of the key is different depending upon the key with which the hammer is to be engaged, the timing of detaching the hammer from the key (or the depth of the key depression) is different according to the length of the key. The difference in the timing of detaching the hammer from the key is considered to give influence to the key touch feeling. However, the conventional keyboard device does not consider this point. 
     The present invention is accomplished to solve the problem involved with the appearance of the keyboard device, out of the problems of the conventional keyboard device. Specifically, the present invention aims to provide a keyboard device for an electronic musical instrument having an appearance similar to an appearance of a keyboard device for an acoustic piano. For easy understanding of the present invention, a numeral of a corresponding portion in an embodiment is written in a parenthesis in the description below of each constituent of the present invention. However, each constituent of the present invention should not be construed as being limited to the corresponding portion indicated by the numeral in the embodiment. 
     In order to attain the foregoing object, the present invention provides a keyboard device for an electronic musical instrument, the keyboard device including: plural white keys and black keys ( 111   w ,  111   b ) that are supported by a key support portion (Kw 1 ,  113   w   1 , Kb 1 ,  113   b   1 ) in order that front ends thereof rock in a vertical direction by a key depression/release operation by a performer, each white key having an edge line extending in a longitudinal direction on a crossing portion of a side face and a top face, and each black key having an edge line extending in the longitudinal direction on a crossing portion of a lower side face and an upper side face tilting inward with respect to the lower side face, wherein each of plural white keys and each of black keys include an operation portion that is depressed and released by the performer, and a drive portion ( 111   w   1 ,  111   b   1 ) extending downward, and a length from the front end of the operation portion to the key support portion is different among the plural white keys and black keys; plural hammers ( 116   w ,  116   b ), each of which is engaged with the drive portion of each of the plural white keys and the drive portion of each of the plural black keys, and each of which is supported by a hammer support portion (Hw 1 ,  118   w   1 , Hb 1 ,  118   b   1 ) in order to rock with the rocking movement of each of the plural white keys and black keys; and a restricting member ( 120 ,  121 ) that restricts the rocking movement of the plural hammers in order to restrict the rocking range of the plural white keys and the plural black keys, wherein a vertical length of the drive portion of a first key and a vertical length of the drive portion of a second key are set to be the same, the first key and the second key being both the white keys or both the black keys out of the plural white keys and the plural black keys, and the vertical position of the hammer support portion of the first hammer engaged with the first key and the vertical position of the hammer support portion of the second hammer engaged with the second key are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion, in order that the vertical positions of the front ends of the operation portions of the first key and the second key become the same in a state in which the first key and the second key are released. In a state in which stopping force of stopping the hammer by the restricting member is transmitted through the engagement portion between the key and the hammer, it is regarded that the rocking movement of the key is substantially restricted by the restricting member of the hammer. The state in which the key is released means the state where the upward displacement of the front end of the operation portion of the key is restricted. 
     In this case, it is preferable that the drive portion of the first key and the drive portion of the second key are respectively provided posterior to the front end of the operation portion of the first key and the front end of the operation of the second key, the distance from the front end of the operation portion of the first key to the key support portion is longer than the distance from the front end of the operation portion of the second key to the key support portion, and the hammer support portion of the first hammer is located to be higher than the hammer support portion of the second hammer. 
     In this case, it is preferable that the drive portion of the first key and the drive portion of the second key are respectively provided anterior to the front end of the operation portion of the first key and the front end of the operation of the second key, the distance from the front end of the operation portion of the first key to the key support portion is longer than the distance from the front end of the operation portion of the second key to the key support portion, and the hammer support portion of the first hammer is located to be lower than the hammer support portion of the second hammer. 
     In this case, it is preferable that the length from the front end of the operation portion to the back end of the plural white keys becomes shorter toward the high-pitched side from the low-pitched side, and the length from the front end of the operation portion to the back end of the plural black keys becomes shorter toward the high-pitched side from the low-pitched side. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located between the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are released. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located below the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are depressed, and the rocking movements of the first key, the second key, and the black key are restricted. The state in which the rocking movement is restricted means the state where the same load is applied to the front end of the white key and to the front end of the black key, and the rocking movement of the key is restricted, for example. The present invention also includes the case where a part of the edge line of the black key on the front end is located below the top face of the first key and the top face of the second key. 
     According to the present invention, the vertical position of the hammer support portion is set according to the length of the key. With this structure, the vertical position of the engagement point where the key and the hammer are engaged with each other in the key release state is made different, whereby the height of the front end of the first key and the height of the front end of the second key in the key release state can be adjusted to be the same. Accordingly, the keyboard device according to the present invention has an appearance similar to an appearance of an acoustic piano in the key release state. 
     Another aspect of the present invention is a keyboard device for an electronic musical instrument, the keyboard device including: plural white keys and black keys ( 211   w ,  211   b ) that are supported by a key support portion (Kw 2 ,  213   w   1 , Kb 2 ,  213   b   1 ) in order that front ends thereof rock in a vertical direction by a key depression/release operation by a performer, each white key having an edge line extending in a longitudinal direction on a crossing portion of a side face and a top face, and each black key having an edge line extending in the longitudinal direction on a crossing portion of a lower side face and an upper side face tilting inward with respect to the lower side face, wherein each of plural white keys and each of black keys include an operation portion that is depressed and released by the performer, and a drive portion ( 211   w   1 ,  211   b   1 ) extending downward, and a length from the front end of the operation portion to the key support portion is different among the plural white keys and black keys; plural hammers ( 216   w ,  216   b ), each of which includes an engagement portion engaged with the drive portion of each of the plural white keys and the drive portion of each of the plural black keys, and each of which is supported by a hammer support portion (Hw 2 ,  218   w   1 , Hb 2 ,  218   b   1 ) in order to rock with the rocking movement of each of the plural white keys and black keys; and a restricting member ( 220 ,  221 ,  221 A) that restricts the rocking movement of the plural hammers in order to restrict the rocking range of the plural white keys and the plural black keys, wherein a vertical length of the drive portion of a first key and a vertical length of the drive portion of a second key are set to be the same, the first key and the second key being both the white keys or being both the black keys out of the plural white keys and the plural black keys, the longitudinal position and the vertical position of the hammer support portion of the first hammer engaged with the first key and the longitudinal position and the vertical position of the hammer support portion of the second hammer engaged with the second key are set to be the same, and a vertical position of an engagement point of the first key and the first hammer and a vertical position of an engagement point of the second key and the second hammer are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion, in order that the vertical positions of the front ends of the operation portions of the first key and the second key become the same in a state in which the first key and the second key are released. In a state in which stopping force of stopping the hammer by the restricting member is transmitted through the engagement portion between the key and the hammer, it is regarded that the rocking movement of the key is substantially restricted by the restricting member of the hammer. The state in which the key is released means the state where the upward displacement of the front end of the operation portion of the key is restricted. 
     In this case, it is preferable that the restricting member includes an upper-limit stopper ( 221 ,  221 A) restricting an upward rocking movement of the front ends of the first key and the second key, and a position of a contact point between the first hammer and the upper-limit stopper and a position of a contact point between the second hammer and the upper-limit stopper are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion, in order that a rocking angle of the first hammer and a rocking angle of the second hammer in the key release state of the first key and the second key are respectively set to an angle according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the first hammer and the second hammer respectively include a contact portion ( 216   w   3 ,  216   b   3 ) to the upper-limit stopper, the contact portion has a contact surface extending in the longitudinal direction, the contact surface tilts with respect to a mounting surface (FR 2 ) of the upper-limit stopper in the key release state of the first key and the second key, and the longitudinal position of the upper-limit stopper with respect to the contact portion of the first hammer and the longitudinal position of the upper-limit stopper with respect to the contact portion of the second hammer are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion, in order that the vertical position of the contact point between the first hammer and the upper-limit stopper and the vertical position of the contact point between the second hammer and the upper-limit stopper are set to be the same, and that the longitudinal position of the contact point between the first hammer and the upper-limit stopper and the longitudinal position of the contact point between the second hammer and the upper-limit stopper are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the drive portion of each of the plural white keys is provided posterior to the front end of the operation portion of each of the plural white keys, the drive portion of each of the plural black keys is provided anterior to the front end of the operation portion of each of the plural black keys, and a tilting direction of the contact surface of the hammer engaged with the white key and a tilting direction of the contact surface of the hammer engaged with the black key are reverse to each other. 
     In this case, it is preferable that the thickness of the upper-limit stopper ( 221 A) that is in contact with the first hammer and the second hammer is set to be a thickness according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion, in order that the vertical position of the contact point between the first hammer and the upper-limit stopper and the vertical position of the contact point between the second hammer and the upper-limit stopper are respectively set to a position according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the engagement portion of the first hammer and the engagement portion of the second hammer respectively have a base member (Fw 21 , Fw 22 , Fb 21 , Fb 22 ) and a spacer (SP) mounted to the base member, and the thickness of the spacer is set according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the first hammer and the second hammer are bent in the vertical direction on the middle part in the longitudinal direction by a bending process, and a bending amount of the first hammer and the second hammer by the bending process is set according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the length from the front end of the operation portion to the back end of the plural white keys becomes shorter toward the high-pitched side from the low-pitched side, and the length from the front end of the operation portion to the back end of the plural black keys becomes shorter toward the high-pitched side from the low-pitched side. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located between the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are released. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located below the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are depressed, and the rocking movements of the first key, the second key, and the black key are restricted. The state in which the rocking movement is restricted means the state where the same load is applied to the front end of the white key and to the front end of the black key, and the rocking movement of the key is restricted, for example. The present invention also includes the case where a part of the edge line of the black key on the front end is located below the top face of the first key and the top face of the second key. 
     According to the present invention, the vertical position of the engagement point where the key and the hammer are engaged with each other in the key release state is made different by the structure in which the rocking angle of the hammer in the key release state is made different, the thickness of the spacer mounted to the base member is made different, and the bending amount of the hammer in the bending process is made different, whereby the height of the front end of the first key and the height of the front end of the second key in the key release state can be adjusted to be the same. Accordingly, the keyboard device according to the present invention has an appearance similar to an appearance of an acoustic piano in the key release state. 
     Another aspect of the present invention is a keyboard device for an electronic musical instrument, the keyboard device including: plural white keys and black keys ( 311   w ,  311   b ) that are supported by a key support portion (Kw 3 ,  313   w   1 , Kb 3 ,  313   b   1 ) in order that front ends thereof rock in a vertical direction by a key depression/release operation by a performer, each white key having an edge line extending in a longitudinal direction on a crossing portion of a side face and a top face, and each black key having an edge line extending in the longitudinal direction on a crossing portion of a lower side face and an upper side face tilting inward with respect to the lower side face, wherein each of plural white keys and each of black keys include an operation portion that is depressed and released by the performer, and a drive portion ( 311   w   1 ,  311   b   1 ) extending downward, and a length from the front end of the operation portion to the key support portion is different among the plural white keys and black keys; plural hammers ( 316   w ,  316   b ), each of which is engaged with the drive portion of each of the plural white keys and the drive portion of each of the plural black keys, and each of which is supported by a hammer support portion (Hw 3 ,  318   w   1 , Hb 3 ,  318   b   1 ) in order to rock with the rocking movement of each of the plural white keys and black keys; and a restricting member ( 320 ,  321 ) that restricts the rocking movement of the plural hammers in order to restrict the rocking range of the plural white keys and the plural black keys, wherein vertical positions of engagement portions between the plural white keys as well as the plural black keys and the plural hammers are set to be the same in a state in which the plural white keys and the plural black keys are released, and in a state in which a first key and a second key out of the plural white keys and the plural black keys are released, the first key and the second key being both the white keys or being both the black keys, the vertical size of the first key and the vertical size of the second key are respectively set according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion in order that the vertical positions of the front ends of the operation portions of the first key and the second key become the same. In a state in which stopping force of stopping the hammer by the restricting member is transmitted through the engagement portion between the key and the hammer, it is regarded that the rocking movement of the key is substantially restricted by the restricting member of the hammer. The state in which the key is released means the state where the upward displacement of the front end of the operation portion of the key is restricted. 
     In this case, it is preferable that the first key and the second key are configured by combining plural components (Uw, Mw, Lw, Ub, Mb, Lb) in the vertical direction, and the vertical size of one or more components out of the plural components forming the first key and the second key is set according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the plural components forming the first key and the second key include a shock absorbing member (SA) mounted on a lower end of the drive portion, and the thickness of the shock absorbing member is set according to the distance from the front end of the operation portion of the first key to the key support portion and the distance from the front end of the operation portion of the second key to the key support portion. 
     In this case, it is preferable that the length from the front end of the operation portion to the back end of the plural white keys becomes shorter toward the high-pitched side from the low-pitched side, and the length from the front end of the operation portion to the back end of the plural black keys becomes shorter toward the high-pitched side from the low-pitched side. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located between the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are released. 
     In this case, it is preferable that the first key and the second key are adjacent white keys, and the edge line of the black key between the first key and the second key is located below the top face of the first key and the top face of the second key, in a state in which the first key, the second key, and the black key are depressed, and the rocking movements of the first key, the second key, and the black key are restricted. The state in which the rocking movement is restricted means the state where the same load is applied to the front end of the white key and to the front end of the black key, and the rocking movement of the key is restricted, for example. The present invention also includes the case where a part of the edge line of the black key on the front end is located below the top face of the first key and the top face of the second key. 
     According to the present invention, the vertical size of the first key and the vertical size of the second key are set according to the longitudinal length of the first key and the longitudinal length of the second key in order that the height of the front end of the first key and the height of the front end of the second key in the key release state are adjusted to be the same. Accordingly, the keyboard device according to the present invention has an appearance similar to an appearance of an acoustic piano in the key release state. 
     Still another aspect of the present invention is that the distance between a plane including the edge line of the first key and the key support portion of the first key is set to be the same as the distance between a plane including the edge line of the second key and the key support portion of the second key. In this case, it is preferable that the vertical positions of the key support portions of the first key and the second key are set to be the same. With this structure, the parts other than the parts involved with the length of the key can be made common as much as possible. This structure also simplifies the design of the support member (frame) supporting the key. This structure also facilitates the processing of the support member, whereby precision can be enhanced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiment when considered in connection with the accompanying drawings, in which: 
         FIG. 1  is a plan view illustrating a keyboard device according to a first embodiment of the present invention; 
         FIG. 2  is a right side view illustrating a configuration of a white key on a low-pitched side in the keyboard device illustrated in  FIG. 1 ; 
         FIG. 3  is a right side view illustrating a configuration of a white key on a high-pitched side in the keyboard device illustrated in  FIG. 1 ; 
         FIG. 4  is a right side view illustrating a configuration of a black key on a low-pitched side in the keyboard device illustrated in  FIG. 1 ; 
         FIG. 5  is a right side view illustrating a configuration of a black key on a high-pitched side in the keyboard device illustrated in  FIG. 1 ; 
         FIG. 6  is a graph of a characteristic curve illustrating a relationship between a pitch and a mass of a mass member; 
         FIG. 7  is a graph of a characteristic curve illustrating a relationship between a pitch and a key touch; 
         FIG. 8  is a schematic view illustrating a difference in the configuration between the white key on the low-pitched side and the white key on the high-pitched side in  FIG. 1 ; 
         FIG. 9  is a schematic view illustrating a difference in the configuration between the black key on the low-pitched side and the black key on the high-pitched side in  FIG. 1 ; 
         FIG. 10  is a plan view illustrating a keyboard device according to a second embodiment of the present invention; 
         FIG. 11  is a right side view illustrating a configuration of a white key on a low-pitched side in the keyboard device illustrated in  FIG. 10 ; 
         FIG. 12  is a right side view illustrating a configuration of a white key on a high-pitched side in the keyboard device illustrated in  FIG. 10 ; 
         FIG. 13  is a right side view illustrating a configuration of a black key on a low-pitched side in the keyboard device illustrated in  FIG. 10 ; 
         FIG. 14  is a right side view illustrating a configuration of a black key on a high-pitched side in the keyboard device illustrated in  FIG. 10 ; 
         FIG. 15  is a graph of a characteristic curve illustrating a relationship between a pitch and a mass of a mass member; 
         FIG. 16  is a graph of a characteristic curve illustrating a relationship between a pitch and a key touch; 
         FIG. 17  is a schematic view illustrating a difference in the configuration between the white key on the low-pitched side and the white key on the high-pitched side in  FIG. 10 ; 
         FIG. 18  is a schematic view illustrating a difference in the configuration between the black key on the low-pitched side and the black key on the high-pitched side in  FIG. 10 ; 
         FIG. 19  is a plan view illustrating a keyboard device according to a modification of the present invention; 
         FIG. 20  is a right side view illustrating a configuration of a white key on a low-pitched side in the keyboard device illustrated in  FIG. 19 ; 
         FIG. 21  is a right side view illustrating a configuration of a white key on a high-pitched side in the keyboard device illustrated in  FIG. 19 ; 
         FIG. 22  is a right side view illustrating a configuration of a black key on a low-pitched side in the keyboard device illustrated in  FIG. 19 ; 
         FIG. 23  is a right side view illustrating a configuration of a black key on a high-pitched side in the keyboard device illustrated in  FIG. 19 ; 
         FIG. 24  is a right side view illustrating a configuration of a white key in a keyboard device according to another modification of the present invention; 
         FIG. 25  is a right side view illustrating a configuration of a black key in the keyboard device according to another modification of the present invention; 
         FIG. 26  is an enlarged view of the surrounding of the engagement portion according to another modification of the present invention; 
         FIG. 27  is a plan view illustrating a keyboard device according to a third embodiment of the present invention; 
         FIG. 28  is a right side view illustrating a configuration of a white key on a low-pitched side in the keyboard device illustrated in  FIG. 27 ; 
         FIG. 29  is a right side view illustrating a configuration of a white key on a high-pitched side in the keyboard device illustrated in  FIG. 27 ; 
         FIG. 30  is a right side view illustrating a configuration of a black key on a low-pitched side in the keyboard device illustrated in  FIG. 27 ; 
         FIG. 31  is a right side view illustrating a configuration of a black key on a high-pitched side in the keyboard device illustrated in  FIG. 27 ; 
         FIG. 32  is a graph of a characteristic curve illustrating a relationship between a pitch and a mass of a mass member; 
         FIG. 33  is a graph of a characteristic curve illustrating a relationship between a pitch and a key touch; 
         FIG. 34  is a schematic view illustrating a difference in the configuration between the white key on the low-pitched side and the white key on the high-pitched side in  FIG. 27 ; 
         FIG. 35  is a schematic view illustrating a difference in the configuration between the black key on the low-pitched side and the black key on the high-pitched side in  FIG. 27 ; 
         FIG. 36A  is a side view illustrating a configuration of a white key according to a modification of the present invention; 
         FIG. 36B  is a side view illustrating a configuration of a black key according to a modification of the present invention; and 
         FIG. 37  is an enlarged view of an engagement portion where a key and a hammer are engaged with each other. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment of the present invention will be described below with reference to the drawings. In the description below, a side close to a performer is defined as a “front side”, while a side far from the performer is defined as a “rear side”. A high-pitched side is defined as a “right side”, while a low-pitched side is defined as a “left side”. 
     A keyboard device includes plural white keys  111   w  and plural black keys  111   b  as illustrated in  FIG. 1 . A different pitch is assigned to each of plural white keys  111   w  and each of plural black keys  111   b . In the present embodiment, one of “C 3 ”, “D 3 ”, . . . “C 6 ” is assigned to the white keys  111   w , while one of “C# 3 ”, “D# 3 ”, “B# 5 ” is assigned to the black keys  111   b . The white keys  111   w  and black keys  111   b  are integrally formed to have a long shape by a synthetic resin. The white keys  111   w  are configured such that the length thereof is gradually shorter toward the white key  111   w  on the high-pitched side from the white key  111   w  on the low-pitched side. The black keys  111   b  are configured such that the length thereof is gradually shorter toward the black key  111   b  on the high-pitched side from the black key  111   b  on the low-pitched side. The back end of the black key  111   b  is located posterior to the back end of the adjacent white key  111   w.    
     The white keys  111   w , each having a different assigned pitch, have different length in the longitudinal direction, but the other structures are the same. The black keys  111   b , each having a different assigned pitch, have different length in the longitudinal direction, but the other structures are the same. Each of the white keys  111   w  has a width in the vertical direction smaller than that of the black key  111   b , and has a width in the lateral direction larger than that of the black key  111   b , as illustrated in  FIGS. 2 to 5 . The white key  111   w  and the black key  111   b  have a hollow shape including a thin top wall extending in the longitudinal direction, and thin sidewalls extending downward from left and right ends of the top wall respectively, with no bottom. 
     Through-holes Kw 1  and Kb 1  that are opposite to each other are formed on the rear part of the sidewall of the white key  111   w  and the black key  111   b . The distance from the through-holes Kw 1  and Kb 1  to the back end of each key is the same for all keys. The white key  111   w  and the black key  111   b  are supported by a key support portion  113   w  and a key support portion  113   b  of a later-described key frame  112  with the through-holes Kw 1  and Kb 1 . In the key release state, the white key  111   w  and the black key  111   b  tilt such that the back end becomes lower than the front end. The back end of the white key  111   w  goes into a casing of the electronic musical instrument, when the keyboard device is assembled to the electronic musical instrument. The portion of the white key anterior to the portion going into the casing is referred to as an apparent portion of the white key  111   w . An edge line is formed on the portion where the side face and the top face of the white key  111   w  cross each other. The black key  111   b  has a portion projecting upward from the top face of the white key  111   w  in a state in which the black key  111   b  is not depressed, and the adjacent white keys  111   w  are not depressed. The projecting portion is referred to as an apparent portion of the black key  111   b . The portion lower than the apparent portion of the black key  111   b  is referred to as a body. A performer depresses or releases the apparent portions of the white key  111   w  and the black key  111   b . Specifically, the apparent portion corresponds to an operation portion in the present invention. The width of the apparent portion of the black key  111   b  in the lateral direction becomes narrower toward the top end, and the width of the body in the lateral direction is the same. Specifically, the side face of the apparent portion tilts inward with respect to the side face of the body. An edge line R 1  is formed on the boundary between the apparent portion of the black key  111   b  and the body (see  FIGS. 4 and 5 ). 
     The key frame  112  has a top plate  112   a  extending in the longitudinal direction and lateral direction. The position of the front end of the top plate  112   a  at the low-pitched side and the position of the front end at the high-pitched side are the same, but the back end at the low-pitched side is located posterior to the back end at the high-pitched side. The key frame  112  also has a front plate  112   b  vertically extending downward from the front end of the top plate  112   a , a bottom plate  112   c  horizontally extending from the lower end of the front plate  112   b , and a front plate  112   d  vertically extending upward from the front end of the bottom plate  112   c . The key frame  112  also includes a rear plate  112   e  vertically extending downward from the back end of the top plate  112   a , and a bottom plate  112   f  horizontally extending rearward from the lower end of the rear plate  112   e . The height of the lower surface of the bottom plate  112   c  and the height of the lower surface of the bottom plate  112   f  are the same. The keyboard device is supported by a frame FR 1  of an electronic musical instrument by the structure in which the lower surface of the bottom plate  112   c  and the lower surface of the bottom plate  112   f  are brought into contact with the frame FR 1  of the electronic musical instrument and fixed thereto. The above-described key support portion  113   w  and the key support portion  113   b  are formed to project upward from the upper surface of the top plate  112   a . The key support portion  113   b  is located posterior to the adjacent key support portion  113   w . The key support portion  113   w  and the key support portion  113   b  respectively include two opposing plates, and a projection  113   w   1  and projection  113   b   1  that project inward. The projections  113   w   1  and  113   b   1  are fitted to the through-holes Kw 1  and Kb 1  respectively. Therefore, the white key  111   w  and the black key  111   b  are supported to be rotatable about the projections  113   w   1  and  113   b   1 , and their front ends can rock in the vertical direction with the center axes of the through-holes Kw 1  and Kb 1  and the projections  113   w   1  and the projections  113   b   1  being defined as a pivot center. The position of the projection  113   w   1  and the position of the projection  113   b   1  in the vertical direction are the same for all key support portions. Specifically, the height of the pivot center is the same for all keys. The distance between the top face of the apparent portion of the white key  111   w  (i.e., the plane including the right and left edge lines of the white key  111   w ) and its pivot center in the vertical direction is the same for all white keys  111   w . The distance between the top face of the operation portion of the black key  111   b  (i.e., the plane including the right and left edge lines of the black key  111   b ) and its pivot center in the vertical direction is the same for all black keys  111   b.    
     A drive portion  111   w   1  extends downward from the middle portion of the apparent portion of the white key  111   w . The drive portion  111   w   1  has a hollow shape including a thin front wall extending in the vertical direction, and thin sidewalls extending rearward from left and right ends of the front wall, with no rear wall. The lower end of the drive portion  111   w   1  is closed by a lower end wall. The length of the drive portion  111   w   1  in the vertical direction is the same for all white keys  111   w . On the other hand, the black key  111   b  also has a drive portion  111   b   1  same as the drive portion  111   w   1  of the white key  111   w . The drive portion  111   b   1  has a connection portion that extends downward from the front end of the apparent portion of the black key  111   b  and that is slightly curved to the front, and a vertical portion projecting downward from the leading end of the connection portion. The configuration of the vertical portion is the same for the drive portion  111   w   1 . The length of the drive portion  111   b   1  in the vertical direction is the same for all black keys  111   b.    
     A distance Lw 11  from the front end of the white key  111   w  to the drive portion  111   w   1  in the longitudinal direction is within 30% of a distance Lw 12  from the front end of the white key  111   w  with the highest pitch (i.e., the shortest key of the plural white keys  111   w ) to the through-hole Kw 1 . The distance Lw 11  is the same for all white keys  111   w . A distance Lb 11  from the front end of the apparent portion of the black key  111   b  to the drive portion  111   b   1  in the longitudinal direction is within 30% of a distance Lb 12  from the front end of the apparent portion of the black key  111   b  with the highest pitch (e.g., the shortest key of the plural black keys  111   b ) to the through-hole Kb 1 . The distance Lb 11  is the same for all black keys  111   b . The position of the drive portion  111   w   1  and the position of the drive portion  111   b   1  in the longitudinal direction in the key-released state of the white key  111   w  and the black key  111   b  are the same. Specifically, the drive portions  111   w   1  and the drive portions  111   b   1  are located anterior to the front end of the apparent portion of the black keys  111   b , and the drive portions  111   w   1  and the drive portions  111   b   1  are arranged in the lateral direction. 
     The lower ends of the drive portion  111   w   1  and the drive portion  111   b   1  are respectively engaged with front ends of hammers  116   w  and  116   b  in the opening formed between the front plate  112   b  and the front plate  112   d . As described in detail later, the hammer  116   w  and the hammer  116   b  rock with the rocking movement of the corresponding white key  111   w  and the black key  111   b  with which the respective hammers  116   w  and  116   b  are engaged. 
     The hammer  116   w  includes a base  116   w   1  made of synthetic resin, a connection rod  116   w   2  made of metal, and a mass member  116   w   3 . Like the hammer  116   w , the hammer  116   b  includes a base  116   b   1 , a connection rod  116   b   2 , and a mass member  116   b   3 . The base  116   w   1  and the base  116   b   1  are plate-like members, and formed with through-holes Hw 1  and Hb 1 , respectively, from the right side face to the left side face. A hammer support portion  118   w  and a hammer support portion  118   b  are formed to project downward from the lower surface of the top plate  112   a . The hammer support portions  118   w  and  118   b  are formed to have two opposing plates, and respectively have projections  118   w   1  and  118   b   1  projecting inward. The projections  118   w   1  and  118   b   1  are respectively fitted to the through-holes Hw 1  and Hb 1 . With this structure, the bases  116   w   1  and  116   b   1  are supported to be rotatable about the projections  118   w   1  and  118   b   1 . Specifically, the hammer  116   w  and the hammer  116   b  are supported such that the front ends and the back ends can be rocked in the vertical direction. The positions of the hammer support portion  118   w  and the hammer support portion  118   b  in the longitudinal direction and in the vertical direction are the same for all hammer support portions  118   w  and  118   b . The positions of the projections  118   w   1  and  118   b   1  in the longitudinal direction are the same for all hammer support portions  118   w  and hammer support portions  118   b . The projection  118   w   1  of the hammer support portion  118   w  of the hammer  116   w  for the white key  111   w  to which the higher pitch is assigned is located on a lower position. The projection  118   b   1  of the hammer support portion  118   b  of the hammer  116   b  for the black key  111   b  to which the higher pitch is assigned is located on a higher position. 
     The base  116   w   1  includes a pair of leg portion Fw 11  and leg portion Fw 12  on its front end. The upper leg portion Fw 11  is formed to be shorter than the lower leg portion Fw 12 . Like the base  116   w   1 , the base  116   b   1  includes a pair of leg portion Fb 11  and leg portion Fb 12  on its front end. An elongated slit-like opening  112   b   1  extending in the vertical direction is formed on the front plate  112   b  for each of the hammers  116   w  and  116   b . The front end of each hammer  116   w  and the front end of each hammer  116   b  project forward of the front plate  112   b  through the opening  112   b   1 . The wall of the lower end of the drive portion  111   w   1  enters between the leg portions Fw 11  and Fw 12 , while the wall of the lower end of the drive portion  111   b   1  enters between the leg portions Fb 11  and Fb 12 . Specifically, the leg portions Fw 11  and Fb 11  enter between the walls of the lower ends of the drive portions  111   w   1  and  111   b   1  and intermediate walls that form gaps with the walls of the lower ends in the drive portions  111   w   1  and  111   b   1 . Shock absorbing members such as rubber, urethane, or felt are fitted and fixed on the wall of the lower end of each of the drive portions  111   w   1  and  111   b   1 . The shock absorbing members attenuates shock caused by the collision between the lower end of the drive portion  111   w   1  and the upper surface of the leg portion Fw 12 , the collision between the lower end of the drive portion  111   b   1  and the upper surface of the leg portion Fb 12 , the collision between the lower end of the drive portion  111   w   1  and the lower surface of the leg portion Fw 11 , and the collision between the lower end of the drive portion  111   b   1  and the lower surface of the leg portion Fb 11 . 
     The front end of the connection rod  116   w   2  and the front end of the connection rod  116   b   2  are assembled to the back end of the base  116   w   1  and the back end of the base  116   b   1 , respectively. The connection rods  116   w   2  and  116   b   2  extend rearward. The position of the back end of the connection rod  116   w   2  and the position of the back end of the connection rod  116   b   2  in the longitudinal direction are the same. The mass member  116   w   3  and the mass member  116   b   3 , described later, are assembled to the back end of the connection rod  116   w   2  and the back end of the connection rod  116   b   2 , respectively. 
     The mass member  116   w   3  and the mass member  116   b   3  are formed to have a plate-like shape. The mass member  116   w   3  and the mass member  116   b   3  are long in the longitudinal direction. The mass member  116   w   3  and the mass member  116   b   3  are assembled to the connection rods  116   w   2  and  116   b   2  in such a manner that the thickness thereof is along the lateral direction. In the key release state, the lower surface of the mass member  116   w   3  tilts with respect to the top surface of the frame FR 1 , and the back side of the lower surface of the mass member  116   w   3  is located to be higher than the front side. In the key release state, the lower surface of the mass member  116   b   3  tilts with respect to the top surface of the frame FR 1 , and the back side of the lower surface of the mass member  116   b   3  is located to be higher than the front side. In the key depression state, the top surfaces of the mass member  116   w   3  and the mass member  116   b   3  are parallel to the lower surface of the top plate  112   a  of the key frame  112 . The appearance of the mass member  116   w   3  is the same for all hammers  116   w . The appearance of the mass member  116   b   3  is also the same for all hammers  116   b.    
     As described above, the position of the pivot point of the key is different depending upon the assigned pitch. Therefore, the distance from the pivot center of the white key  111   w  to an engagement portion Pw 11  where the leg portion Fw 12  and the drive portion  111   w   1  are engaged with each other (brought into contact with each other) is different depending upon the assigned pitch. The distance from the pivot center of the black key  111   b  to an engagement portion Pb 11  where the leg portion Fb 12  and the drive portion  111   b   1  are engaged with each other (brought into contact with each other) is also different depending upon the assigned pitch. A key depression/release operation position W 10  of the white key  111   w  that is the front end of the position of the white key  111   w  with the potentiality of being depressed or released is located anterior to the engagement portion Pw 11 , while a key depression/release operation position B 10  of the black key  111   b  that is the front end of the position of the black key  111   b  with the potentiality of being depressed or released is located posterior to the engagement portion Pb 11 . Therefore, if the masses of the mass members for all hammers are equal, a key touch feeling is heavier on the middle-pitched part than on the low-pitched part, and the key touch feeling is heavier on the high-pitched part than on the middle-pitched part, on the key depression/release operation positions W 10  and B 10 , because of the principle of leverage. 
     In addition, in this case, the key touch feeling of the white keys  111   w  and the black keys  111   b  in each range is not equal. Specifically, the key touch feeling of the black key  111   b  is heavier than the key touch feeling of the adjacent two white keys  111   w . In view of this, the mass of the mass member  116   w   3  and the mass of the mass member  116   b   3  are adjusted for each key as illustrated in  FIG. 6 . Specifically, as illustrated in a characteristic curve indicating the masses of the mass members  116   w   3  and  116   b   3  in the order of pitches, the masses of the mass members  116   w   3  and  116   b   3  are adjusted such that the characteristic curve of the mass member  116   w   3  and the characteristic curve of the mass member  116   b   3  are parallel downward-sloping curves, wherein the characteristic curve of the mass member  116   b   3  is located below the characteristic curve of the mass member  116   w   3 . Thus, as illustrated by a chain line in  FIG. 7 , the key touch feeling on the key depression/release operation positions W 10  and B 10  becomes gradually lighter toward the high-pitched side from the low-pitched side. Therefore, as illustrated by a broken line in  FIG. 7 , the key touch feeling on key depression/release operation positions W 11  and B 11  located posterior to the key depression/release operation positions W 10  and B 10  by a distance d 1  also becomes gradually lighter toward the high-pitched side from the low-pitched side. Since the length of the key to which a higher pitch is assigned is shorter, the difference between the key touch feeling on the key depression/release operation positions W 10  and B 10  and the key touch feeling on the key depression/release operation positions W 11  and B 11  becomes larger toward the high-pitched side from the low-pitched side. Specifically, the difference in the key touch feeling caused by the longitudinal difference of the key depression/release operation position is small on the low-pitched side, moderate in the middle-pitched side, and large on the high-pitched side. 
     When the white key  111   w  and the black key  111   b  are released, the front ends of the hammers  116   w  and  116   b  displace upward due to their own weight of the hammers  116   w  and  116   b . In this case, the drive portion  111   w   1  and the drive portion  111   b   1  are biased upward by the leg portion Fw 12  and the leg portion Fb 12  respectively, whereby the front ends of the white key  111   w  and the black key  111   b  displace upward. On the other hand, when the white key  111   w  and the black key  111   b  are depressed, the lower surfaces of the drive portion  111   w   1  and the drive portion  111   b   1  press the upper surfaces of the leg portion Fw 12  and the leg portion Fb 12  respectively, whereby the front ends of the hammer  116   w  and the hammer  116   b  respectively displace downward. 
     A lower-limit stopper  120  is provided to the key frame  112 . During the key depression, the lower-limit stopper  120  is brought into contact with the upper surfaces of the mass member  116   w   3  and the mass member  116   b   3  of the hammer  116   w  and the hammer  116   b  so as to restrict the upward displacement of the back ends of the hammer  116   w  and the hammer  116   b , thereby restricting the downward displacement of the front ends of the white key  111   w  and the black key  111   b . The lower-limit stopper  120  includes a stopper rail  120   a  and a buffer member  120   b . The stopper rail  120   a  protrudes downward from the lower surface at the middle of the top plate  112   a , and extends parallel to the arrangement direction of the keys. The projection amount of the stopper rail  120   a  from the lower surface of the top plate  112   a  on the contact portion between the stopper rail  120   a  and each hammer is constant in the lateral direction. The buffer member  120   b  is fixed to the lower end surface of the stopper rail  120   a . The buffer member  120   b  is a long member made of a shock-absorbing member such as rubber or felt. The sectional shape of the buffer member  120   b  is uniform from one end to the other end. 
     An upper-limit stopper  121  is provided to the middle portion of the frame FR 1 . During the key release, the upper-limit stopper  121  is brought into contact with the lower surfaces of the mass member  116   w   1  and the mass member  116   b   1  of the hammer  116   w  and the hammer  116   b  so as to restrict the downward displacement of the back ends of the hammer  116   w  and the hammer  116   b , thereby restricting the upward displacement of the front ends of the white key  111   w  and the black key  111   b . Like the lower-limit stopper  120 , the upper-limit stopper  121  includes a stopper rail  121   a  and a buffer member  121   b . Specifically, the stopper rail  121   a  also extends parallel to the arrangement direction of the keys, and the projection amount thereof from the frame FR 1  is constant in the lateral direction. The buffer member  121   b  is fixed on the upper surface of the stopper rail  121   a . Like the buffer member  120   b , the sectional shape of the buffer member  121   b  is uniform from one end to the other end. The stopper rail  120   a  and the stopper rail  121   a  may continuously extend in the lateral direction, or may discontinuously extend. The stopper rail  120   a  and the stopper rail  121   a  may be formed integral with the top plate  112   a  and the frame FR 1  respectively, or may be formed as separate components and assembled to the top plate  112   a  and the frame FR 1  respectively. 
     As described above, the projection  118   w   1  of the hammer support portion  118   w  of the hammer  116   w  for the white key  111   w  to which a higher pitch is assigned is located on a lower position. Therefore, during the key release, the engagement portion Pw 11  between the hammer  116   w  and the drive portion  111   w   1  on the high-pitched side is located to be lower than the engagement portion Pw 11  between the hammer  116   w  and the drive portion  111   w  on the low-pitched side. 
     As described above, the white key  111   w  tilts such that the back end is lower than the front end during the key release. The length of the drive portion  111   w   1  in the vertical direction is the same for all white keys  111   w . The height of the pivot center is the same for all white keys  111   w . Accordingly, if the position of the engagement portion Pw 11  in the vertical direction is the same during the key release, the front end of the white key  111   w  having the shorter length in the longitudinal direction might become high. In view of this, in the present embodiment, the projection  118   w   1  of the hammer support portion  118   w  of the hammer  116   w  for the white key  111   w  to which a higher pitch is assigned is located on a lower position. With this structure, the engagement portion Pw 11  of the white key  111   w  on the high-pitched side is located to be lower than the engagement portion Pw 11  of the white key  111   w  on the low-pitched side, whereby the height of the front ends of all white keys  111   w  is adjusted to be the same (see  FIG. 8 ). Specifically, the position of the projection  118   w   1  in the vertical direction is set according to the length of the white key  111   w  in order to adjust the height of the front ends of all white keys  111   w  during the key release to be the same. 
     As described above, the projection  118   b   1  of the hammer support portion  118   b  of the hammer  116   b  for the black key  111   b  to which a higher pitch is assigned is located on a higher position. Therefore, during the key release, the engagement portion Pb 11  between the hammer  116   b  and the drive portion  111   b   1  on the high-pitched side is located to be higher than the engagement portion Pb 11  between the hammer  116   b  and the drive portion  111   b  on the low-pitched side. 
     As described above, the black key  111   b  tilts such that the back end is lower than the front end during the key release. The length of the drive portion  111   b   1  in the vertical direction is the same for all black keys  111   b . The height of the pivot center is the same for all black keys  111   b . Accordingly, if the position of the engagement portion Pb 11  in the vertical direction is the same during the key release, the front end of the black key  111   b  having the shorter length in the longitudinal direction might become low. In view of this, in the present embodiment, the projection  118   b   1  of the hammer support portion  118   b  of the hammer  116   b  for the black key  111   b  to which a higher pitch is assigned is located on a higher position. With this structure, the engagement portion Pb 11  of the black key  111   b  on the high-pitched side is located to be higher than the engagement portion Pb 11  of the black key  111   b  on the low-pitched side, whereby the height of the front ends of all black keys  111   b  is adjusted to be the same (see  FIG. 9 ). Specifically, the position of the projection  118   b   1  in the vertical direction is set according to the length of the black key  111   b  in order to adjust the height of the front ends of all black keys  111   b  during the key release to be the same. 
     In a state in which two adjacent white keys  111   w  and the black key  111   b  between the two adjacent white keys  111   w  are released, the rocking angle of each hammer is set such that the edge line R 1  of the black key  111   b  is located below the top face of one on the low-pitched side of the two white keys  111   w , and above the top face of one on the high-pitched side of the two white keys  111   w.    
     The rocking angle of each hammer is set such that, in the state in which the white key  111   w  and the black key  111   b  adjacent to the white key  111   w  are depressed respectively by the same depression force, and their rocking movement is restricted, the edge line R 1  of the black key  111   b  is located below the top face of the white key  111   w . The buffer member  120   b  and the buffer member  121   b  have elasticity. Therefore, when the key is depressed more after the hammer is brought into the buffer member during the key depression, the buffer member is elastically deformed, so that the front end of the key slightly displaces downward. 
     A switch drive portion AC 11  is provided on the lower surface of each of the white key  111   w  and the black key  111   b  on the middle part. The switch drive portion AC 11  is a plate-like member extending in the vertical direction in each of the white key  111   w  and the black key  111   b , and the lower end surface of the switch drive portion AC 11  is brought into contact with the upper surface of a switch SW 11 . The switch SW 11  is provided for each key. The switch SW 11  is pressed by the corresponding key to detect whether the corresponding key is depressed or released. Specifically, when the switch SW 11  is depressed by the key, a rubber main body is deformed to make two contacts, which are formed on a circuit board  123 , short-circuit, thereby being turned ON. The circuit board  123  extends in the lateral direction. Through-holes penetrating from the upper surface to the lower surface are formed on the circuit board  123 . The through-holes correspond to a bosses  124  formed integral with the upper surface of the top plate  112   a . When screws are threaded to the bosses  124  through the through-holes, the circuit board  123  is fixed to the key frame  112 . The main bodies of the plural switches SW 11 , each corresponding to each key, are arranged on the upper surface of the circuit board  123  in the lateral direction. The position of the switch SW 11  for the white key  111   w  and the position of the switch SW 11  for the black key  111   b  in the longitudinal direction are the same. A distance Lw 13  from the front end of the white key  111   w  to the switch SW 11  in the longitudinal direction is within 30% of the distance Lw 12  from the front end of the white key  111   w  with the highest pitch to the through-hole Kw 1 , and a distance Lb 13  from the front end of the apparent portion of the black key  111   b  to the switch SW 11  is within 30% of the distance Lb 12  from the front end of the apparent portion of the black key  111   b  with the highest pitch to the through-hole Kb 1 . The switch SW 11  for the white key  111   w  and the switch SW 11  for the black key  111   b  may be arranged side by side in the lateral direction, and the positions of both switches in the longitudinal direction may be shifted. 
     A key guide  125   w  for guiding the rocking movement of the white key  111   w  is formed to project upward from the top end surface of the front plate  112   d . The key guide  125   w  is inserted into the white key  111   w  from below, and during the key depression and key release, the side face of the key guide  125   w  and the inside face of the sidewall of the white key  111   w  are in sliding contact with each other. This structure can prevent a slight displacement of the white key  111   w  in the lateral direction during the key depression and key release. 
     A key guide  125   b  for guiding the rocking movement of the black key  111   b  is formed to project upward from the upper surface of the top plate  112   a  at the front end. The key guide  125   b  is inserted into the black key  111   b  from below, and during the key depression and key release, the side face of the key guide  125   b  and the inside face of the sidewall of the black key  111   b  are in sliding contact with each other. This structure can prevent a slight displacement of the black key  111   b  in the lateral direction during the key depression and key release. 
     In the keyboard device having the configuration described above, the height of the front ends of the keys during the key release is adjusted to be the same, whereby the appearance of the key board device can be made similar to the appearance of the keyboard device for an acoustic piano during the key release. In addition, the keyboard device according to the present embodiment has high productivity, compared to the keyboard device for an acoustic piano in which the height of the front ends of the keys is adjusted to be the same by adjusting the number or the thickness of spacer, which is sandwiched between the key support portion and the frame. 
     The distance from the top face of the apparent portion of the white key  111   w  to the pivot center is the same for all white keys  111   w , and the distance from the top face of the body of the black key  111   b  to the pivot center is the same for all black keys  111   b . Accordingly, when the through-holes Kw 1  and Kb 1  are formed in a different process after a process of molding the outer shape of the white key  111   w  and the black key  111   b , the different process can commonly be carried out for all keys to enhance productivity of the keys. The positions of the projections  113   w   1  and  113   b   1  of the key support portions  113   w  and  113   b  in the vertical direction are set to be the same for all key support portions  113   w  and  113   b , resulting in that the frame  112  that supports the keys is easily designed. In addition, the frame  112  is easily processed, and the precision can be enhanced. 
     In the embodiment described above, the white key  111   w  and the black key  111   b  are supported by the key support portions  113   w  and  113   b  of the key frame  112  by fitting the projections  113   w   1  and  113   b   1  to the through-holes Kw 1  and Kb 1  respectively so that the front ends of the white key  111   w  and the black key  111   b  can rock in the vertical direction. However, the white key  111   w  and the black key  111   b  can be mounted on the key frame  112  by using various supporting mechanisms, if the white key  111   w  and the black key  111   b  are supported by the key frame  112  so that the front ends of the white key  111   w  and the black key  111   b  can rock in vertical direction. For example, the rear ends of plural keys (the white key  111   w  and/or the black key  111   b ) may be are supported by the key frame  112  through elastic deformation members so that the front ends of the plural keys can rock in vertical direction. Concretely, the rear ends of the plural keys are connected to a fixing member fixed to the key frame  112  through thin and elastic connection members, wherein the fixing member is extended in the lateral direction, the connection members are extended horizontally or vertically, and the plural keys, the connection members and the fixing member are formed integrally. In this case, for example, the connection members for the white keys  111   w  are extended horizontally, and the connection members for the black keys  111   b  are extended vertically. 
     Subsequently, a second embodiment of the present invention will be described below with reference to the drawings. In the description below, a side close to a performer is defined as a “front side”, while a side far from the performer is defined as a “rear side”. A high-pitched side is defined as a “right side”, while a low-pitched side is defined as a “left side”. 
     A keyboard device includes plural white keys  211   w  and plural black keys  211   b  as illustrated in  FIG. 10 . A different pitch is assigned to each of plural white keys  211   w  and each of plural black keys  211   b . In the present embodiment, one of “C 3 ”, “D 3 ”, . . . “C 6 ” is assigned to the white keys  211   w , while one of “C# 3 ”, “D# 3 ”, “B# 5 ” is assigned to the black keys  211   b . The white keys  211   w  and black keys  211   b  are integrally formed to have a long shape by a synthetic resin. The white keys  211   w  are configured such that the length thereof is gradually shorter toward the white key  211   w  on the high-pitched side from the white key  211   w  on the low-pitched side. The black keys  211   b  are configured such that the length thereof is gradually shorter toward the black key  211   b  on the high-pitched side from the black key  211   b  on the low-pitched side. The back end of the black key  211   b  is located posterior to the back end of the adjacent white key  211   w.    
     The white keys  211   w , each having a different assigned pitch, have different length in the longitudinal direction, but the other structures are the same. The black keys  211   b , each having a different assigned pitch, have different length in the longitudinal direction, but the other structures are the same. Each of the white keys  211   w  has a width in the vertical direction smaller than that of the black key  211   b , and has a width in the lateral direction larger than that of the black key  211   b , as illustrated in  FIGS. 11 to 14 . The white key  211   w  and the black key  211   b  have a hollow shape including a thin top wall extending in the longitudinal direction, and thin sidewalls extending downward from left and right ends of the top wall respectively, with no bottom. 
     Through-holes Kw 2  and Kb 2  that are opposite to each other are formed on the rear part of the sidewall of the white key  211   w  and the black key  211   b . The distance from the through-holes Kw 2  and Kb 2  to the back end of each key is the same for all keys. The white key  211   w  and the black key  211   b  are supported by a key support portion  213   w  and a key support portion  213   b  of a later-described key frame  212  with the through-holes Kw 2  and Kb 2 . In the key release state, the white key  211   w  and the black key  211  tilt such that the back end becomes lower than the front end. The back end of the white key  211   w  goes into a casing of the electronic musical instrument, when the keyboard device is assembled to the electronic musical instrument. The portion of the white key anterior to the portion going into the casing is referred to as an apparent portion of the white key  211   w . An edge line is formed on the portion where the side face and the top face of the white key  211   w  cross each other. The black key  211   b  has a portion projecting upward from the top face of the white key  211   w  in a state in which the black key  211   b  is not depressed, and the adjacent white keys  211   w  are not depressed. The projecting portion is referred to as an apparent portion of the black key  211   b . The portion lower than the apparent portion of the black key  211   b  is referred to as a body. A performer depresses or releases the apparent portions of the white key  211   w  and the black key  211   b . Specifically, the apparent portion corresponds to an operation portion in the present invention. The width of the apparent portion of the black key  211   b  in the lateral direction becomes narrower toward the top end, and the width of the body in the lateral direction is the same. Specifically, the side face of the apparent portion tilts inward with respect to the side face of the body. An edge line R 2  is formed on the boundary between the apparent portion of the black key  211   b  and the body (see  FIGS. 13 and 14 ). 
     The key frame  212  has a top plate  212   a  extending in the longitudinal direction and lateral direction. The position of the front end of the top plate  212   a  at the low-pitched side and the position of the front end at the high-pitched side are the same, but the back end at the low-pitched side is located posterior to the back end at the high-pitched side. The key frame  212  also has a front plate  212   b  vertically extending downward from the front end of the top plate  212   a , a bottom plate  212   c  horizontally extending from the lower end of the front plate  212   b , and a front plate  212   d  vertically extending upward from the front end of the bottom plate  212   c . The key frame  212  also includes a rear plate  212   e  vertically extending downward from the back end of the top plate  212   a , and a bottom plate  212   f  horizontally extending rearward from the lower end of the rear plate  212   e . The height of the lower surface of the bottom plate  212   c  and the height of the lower surface of the bottom plate  212   f  are the same. The keyboard device is supported by a frame FR 2  of an electronic musical instrument by the structure in which the lower surface of the bottom plate  212   c  and the lower surface of the bottom plate  212   f  are brought into contact with the frame FR 2  of the electronic musical instrument and fixed thereto. The above-described key support portion  213   w  and the key support portion  213   b  are formed to project upward from the upper surface of the top plate  212   a . The key support portion  213   b  is located posterior to the adjacent key support portion  213   w . The key support portion  213   w  and the key support portion  213   b  respectively include two opposing plates, and a projection  213   w   1  and projection  213   b   1  that project inward. The projections  213   w   1  and  213   b   1  are fitted to the through-holes Kw 2  and Kb 2  respectively. Therefore, the white key  211   w  and the black key  211   b  are supported to be rotatable about the projections  213   w   1  and  213   b   1 , and their front ends can rock in the vertical direction with the center axes of the through-holes Kw 2  and Kb 2  and the projections  213   w   1  and the projections  213   b   1  being defined as a pivot center. The position of the projection  213   w   1  and the position of the projection  213   b   1  in the vertical direction are the same for all key support portions. Specifically, the height of the pivot center is the same for all keys. The distance between the top face of the apparent portion of the white key  211   w  (i.e., the plane including the right and left edge lines of the white key  211   w ) and its pivot center in the vertical direction is the same for all white keys  211   w . The distance between the top face of the operation portion of the black key  211   b  (i.e., the plane including the right and left edge lines of the black key  211   b ) and its pivot center in the vertical direction is the same for all black keys  211   b.    
     A drive portion  211   w   1  extends downward from the middle portion of the apparent portion of the white key  211   w . The drive portion  211   w   1  has a hollow shape including a thin front wall extending in the vertical direction, and thin sidewalls extending rearward from left and right ends of the front wall, with no rear wall. The lower end of the drive portion  211   w   1  is closed by a lower end wall. The length of the drive portion  211   w   1  in the vertical direction is the same for all white keys  211   w . On the other hand, the black key  211   b  also has a drive portion  211   b   1  same as the drive portion  211   w   1  of the white key  211   w . The drive portion  211   b   1  has a connection portion that extends downward from the front end of the apparent portion of the black key  211   b  and that is slightly curved to the front, and a vertical portion projecting downward from the leading end of the connection portion. The configuration of the vertical portion is the same for the drive portion  211   w   1 . The length of the drive portion  211   b   1  in the vertical direction is the same for all black keys  211   b.    
     A distance Lw 21  from the front end of the white key  211   w  to the drive portion  211   w   1  in the longitudinal direction is within 30% of a distance Lw 22  from the front end of the white key  211   w  with the highest pitch (i.e., the shortest key of the plural white keys  211   w ) to the through-hole Kw 2 . The distance Lw 21  is the same for all white keys  211   w . A distance Lb 21  from the front end of the apparent portion of the black key  211   b  to the drive portion  211   b   1  in the longitudinal direction is within 30% of a distance Lb 22  from the front end of the apparent portion of the black key  211   b  with the highest pitch (e.g., the shortest key of the plural black keys  211   b ) to the through-hole Kb 2 . The distance Lb 21  is the same for all black keys  211   b . The position of the drive portion  211   w   1  and the position of the drive portion  211   b   1  in the longitudinal direction in the key-released state of the white key  211   w  and the black key  211   b  are the same. Specifically, the drive portions  211   w   1  and the drive portions  211   b   1  are located anterior to the front end of the apparent portion of the black keys  211   b , and the drive portions  211   w   1  and the drive portions  211   b   1  are arranged in the lateral direction. 
     The lower ends of the drive portion  211   w   1  and the drive portion  211   b   1  are respectively engaged with front ends of hammers  216   w  and  216   b  in the opening formed between the front plate  212   b  and the front plate  212   d . As described in detail later, the hammer  216   w  and the hammer  216   b  rock with the rocking movement of the corresponding white key  211   w  and the black key  211   b  with which the respective hammers  216   w  and  216   b  are engaged. 
     The hammer  216   w  includes a base  216   w   1  made of synthetic resin, a connection rod  216   w   2  made of metal, and a mass member  216   w   3 . Like the hammer  216   w , the hammer  216   b  includes a base  216   b   1 , a connection rod  216   b   2 , and a mass member  216   b   3 . The base  216   w   1  and the base  216   b   1  are plate-like members, and formed with through-holes Hw 2  and Hb 2 , respectively, from the right side face to the left side face. A hammer support portion  218   w  and a hammer support portion  218   b  are formed to project downward from the lower surface of the top plate  212   a . The hammer support portions  218   w  and  218   b  are formed to have two opposing plates, and respectively have projections  218   w   1  and  218   b   1  projecting inward. The projections  218   w   1  and  218   b   1  are respectively fitted to the through-holes Hw 2  and Hb 2 . With this structure, the bases  216   w   1  and  216   b   1  are supported to be rotatable about the projections  218   w   1  and  218   b   1 . Specifically, the hammer  216   w  and the hammer  216   b  are supported such that the front ends and the back ends can be rocked in the vertical direction. The positions of the hammer support portion  218   w  and the hammer support portion  218   b  in the longitudinal direction and in the vertical direction are the same for all hammer support portions  218   w  and  218   b . Specifically, plural hammer support portions  218   w  and the plural hammer support portions  218   b  are arranged side by side in the lateral direction, and the positions of the pivot centers of all hammers  216   w  and hammers  216   b  in the longitudinal direction and in the vertical direction are the same for all hammers  216   w  and  216   b . In other words, the pivot centers of the hammers  216   w  and the hammers  216   b  are located on the same straight line extending in the lateral direction. 
     The base  216   w   1  includes a pair of leg portion Fw 21  and leg portion Fw 22  on its front end. The upper leg portion Fw 21  is formed to be shorter than the lower leg portion Fw 22 . Like the base  216   w   1 , the base  216   b   1  includes a pair of leg portion Fb 21  and leg portion Fb 22  on its front end. An elongated slit-like opening  212   b   1  extending in the vertical direction is formed on the front plate  212   b  for each of the hammers  216   w  and  216   b . The front end of each hammer  216   w  and the front end of each hammer  216   b  project forward of the front plate  212   b  through the opening  212   b   1 . The wall of the lower end of the drive portion  211   w   1  enters between the leg portions Fw 21  and Fw 22 , while the wall of the lower end of the drive portion  211   b   1  enters between the leg portions Fb 21  and Fb 22 . Specifically, the leg portions Fw 21  and Fb 21  enter between the walls of the lower ends of the drive portions  211   w   1  and  211   b   1  and intermediate walls that form gaps with the walls of the lower ends in the drive portions  211   w   1  and  211   b   1 . A shock absorbing member such as rubber, urethane, or felt is fitted and fixed on the wall of the lower end of each of the drive portions  211   w   1  and  211   b   1 . The shock absorbing member attenuates shock caused by the collision between the lower end of the drive portion  211   w   1  and the upper surface of the leg portion Fw 22 , the collision between the lower end of the drive portion  211   b   1  and the upper surface of the leg portion Fb 22 , the collision between the lower end of the drive portion  211   w   1  and the lower surface of the leg portion Fw 21 , and the collision between the lower end of the drive portion  211   b   1  and the lower surface of the leg portion Fb 21 . 
     The front end of the connection rod  216   w   2  and the front end of the connection rod  216   b   2  are assembled to the back end of the base  216   w   1  and the back end of the base  216   b   1 , respectively. The connection rods  216   w   2  and  216   b   2  extend rearward. The position of the back end of the connection rod  216   w   2  and the position of the back end of the connection rod  216   b   2  in the longitudinal direction are the same. The mass member  216   w   3  and the mass member  216   b   3 , described later, are assembled to the back end of the connection rod  216   w   2  and the back end of the connection rod  216   b   2 , respectively. The mass member  216   w   3  and the mass member  216   b   3  correspond to a contact portion of the present invention, and the lower surface of the mass member  216   w   3  and the lower surface of the mass member  216   b   3  correspond to a contact surface of the present invention. 
     The mass member  216   w   3  and the mass member  216   b   3  are formed to have a plate-like shape. The mass member  216   w   3  and the mass member  216   b   3  are long in the longitudinal direction. The mass member  216   w   3  and the mass member  216   b   3  are assembled to the connection rods  216   w   2  and  216   b   2  in such a manner that the thickness thereof is along the lateral direction. In the key release state, the lower surface of the mass member  216   w   3  tilts with respect to the top surface of the frame FR 2 , and the back side of the lower surface of the mass member  216   w   3  is located to be higher than the front side. In the key release state, the lower surface of the mass member  216   b   3  tilts with respect to the top surface of the frame FR 2 , and the back side of the lower surface of the mass member  216   b   3  is located to be lower than the front side. In the key depression state, the top surfaces of the mass member  216   w   3  and the mass member  216   b   3  are parallel to the lower surface of the top plate  212   a  of the key frame  212 . The appearance of the mass member  216   w   3  is the same for all hammers  216   w . The appearance of the mass member  216   b   3  is also the same for all hammers  216   b.    
     As described above, the position of the pivot point of the key is different depending upon the assigned pitch. Therefore, the distance from the pivot center of the white key  211   w  to an engagement portion Pw 21  where the leg portion Fw 22  and the drive portion  211   w   1  are engaged with each other (brought into contact with each other) is different depending upon the assigned pitch. The distance from the pivot center of the black key  211   b  to an engagement portion Pb 21  where the leg portion Fb 22  and the drive portion  211   b   1  are engaged with each other (brought into contact with each other) is also different depending upon the assigned pitch. A key depression/release operation position W 20  of the white key  211   w  that is the front end of the position of the white key  211   w  with the potentiality of being depressed or released is located anterior to the engagement portion Pw 21 , while a key depression/release operation position B 20  of the black key  211   b  that is the front end of the position of the black key  211   b  with the potentiality of being depressed or released is located posterior to the engagement portion Pb 21 . Therefore, if the masses of the mass members for all hammers are equal, a key touch feeling is heavier on the middle-pitched part than on the low-pitched part, and the key touch feeling is heavier on the high-pitched part than on the middle-pitched part, on the key depression/release operation positions W 20  and B 20 , because of the principle of leverage. 
     In addition, in this case, the key touch feeling of the white keys  211   w  and the black keys  211   b  in each range is not equal. Specifically, the key touch feeling of the black key  211   b  is heavier than the key touch feeling of the adjacent two white keys  211   w . In view of this, the mass of the mass member  216   w   3  and the mass of the mass member  216   b   3  are adjusted for each key as illustrated in  FIG. 15 . Specifically, as illustrated in a characteristic curve indicating the masses of the mass members  216   w   3  and  216   b   3  in the order of pitches, the masses of the mass members  216   w   3  and  216   b   3  are adjusted such that the characteristic curve of the mass member  216   w   3  and the characteristic curve of the mass member  216   b   3  are parallel downward-sloping curves, wherein the characteristic curve of the mass member  216   b   3  is located below the characteristic curve of the mass member  216   w   3 . Thus, as illustrated by a chain line in  FIG. 16 , the key touch feeling on the key depression/release operation positions W 20  and B 20  becomes gradually lighter toward the high-pitched side from the low-pitched side. Therefore, as illustrated by a broken line in  FIG. 16 , the key touch feeling on key depression/release operation positions W 21  and B 21  located posterior to the key depression/release operation positions W 20  and B 20  by a distance d 2  also becomes gradually lighter toward the high-pitched side from the low-pitched side. Since the length of the key to which a higher pitch is assigned is shorter, the difference between the key touch feeling on the key depression/release operation positions W 20  and B 20  and the key touch feeling on the key depression/release operation positions W 21  and B 21  becomes larger toward the high-pitched side from the low-pitched side. Specifically, the difference in the key touch feeling caused by the longitudinal difference of the key depression/release operation position is small on the low-pitched side, moderate in the middle-pitched side, and large on the high-pitched side. 
     When the white key  211   w  and the black key  211   b  are released, the front ends of the hammers  216   w  and  216   b  displace upward due to their own weight of the hammers  216   w  and  216   b . In this case, the drive portion  211   w   1  and the drive portion  211   b   1  are biased upward by the leg portion Fw 22  and the leg portion Fb 22  respectively, whereby the front ends of the white key  211   w  and the black key  211   b  displace upward. On the other hand, when the white key  211   w  and the black key  211   b  are depressed, the lower surfaces of the drive portion  211   w   1  and the drive portion  211   b   1  press the upper surfaces of the leg portion Fw 22  and the leg portion Fb 22  respectively, whereby the front ends of the hammer  216   w  and the hammer  216   b  respectively displace downward. 
     A lower-limit stopper  220  is provided to the key frame  212 . During the key depression, the lower-limit stopper  220  is brought into contact with the upper surfaces of the mass member  216   w   3  and the mass member  216   b   3  of the hammer  216   w  and the hammer  216   b  so as to restrict the upward displacement of the back ends of the hammer  216   w  and the hammer  216   b , thereby restricting the downward displacement of the front ends of the white key  211   w  and the black key  211   b . The lower-limit stopper  220  includes a stopper rail  220   a  and a buffer member  220   b . The stopper rail  220   a  protrudes downward from the lower surface at the middle of the top plate  122   a . In a planar view of the key frame  212 , the stopper rail  220   a  tilts such that the portion on the high-pitched side is located slightly anterior to the portion on the low-pitched side (see  FIG. 10 ). The stopper rail  220   a  may extend parallel to the arrangement direction of the keys. The projection amount of the stopper rail  220   a  from the lower surface of the top plate  212   a  on the contact portion between the stopper rail  220   a  and each hammer is constant in the lateral direction. The buffer member  220   b  is fixed to the lower end surface of the stopper rail  220   a . The buffer member  220   b  is a long member made of a shock-absorbing member such as rubber or felt. The sectional shape of the buffer member  220   b  is uniform from one end to the other end. 
     An upper-limit stopper  221  is provided to the middle portion of the frame FR 2 . During the key release, the upper-limit stopper  221  is brought into contact with the lower surfaces of the mass member  216   w   1  and the mass member  216   b   1  of the hammer  216   w  and the hammer  216   b  so as to restrict the downward displacement of the back ends of the hammer  216   w  and the hammer  216   b , thereby restricting the upward displacement of the front ends of the white key  211   w  and the black key  211   b . Like the lower-limit stopper  220 , the upper-limit stopper  221  includes a stopper rail  221   a  and a buffer member  221   b . Specifically, in a planar view of the key frame  212 , the stopper rail  220   a  tilts such that the portion on the high-pitched side is located slightly anterior to the portion on the low-pitched side (see  FIG. 10 ). The projection amount thereof from the frame FR 2  is constant in the lateral direction. The buffer member  221   b  is fixed on the upper surface of the stopper rail  221   a . Like the buffer member  220   b , the sectional shape of the buffer member  221   b  is uniform from one end to the other end. The stopper rail  220   a  and the stopper rail  221   a  may continuously extend in the lateral direction, or may discontinuously extend. The stopper rail  220   a  and the stopper rail  221   a  may be formed integral with the top plate  212   a  and the frame FR 2  respectively, or may be formed as separate components and assembled to the top plate  212   a  and the frame FR 2  respectively. 
     As described above, the stopper rail  221   a  tilts such that the portion on the low-pitched side is slightly anterior to the portion on the high-pitched side in the planar view of the key frame  212 . Therefore, the contact point between the hammer  216   w  on the high-pitched side ( FIG. 12 ) and the upper-limit stopper  221  is located anterior to the contact point between the hammer  216   w  ( FIG. 11 ) located on the lower-pitched side from the hammer on the high-pitched side and the upper-limit stopper  221 . In the key release state, the rear side of the lower surface of the mass member  216   w   3  is located to be higher than the front side. Therefore, the back end of the hammer  216   w  on the high-pitched side in  FIG. 12  is located on a position higher than the back end of the hammer  216   w  on the low-pitched side in  FIG. 11 . As described above, the top surface of the mass member  216   w   3  is parallel to the lower surface of the top plate  212   a  in the key depression state. Specifically, the lower surface of the lower-limit stopper  220  and the top surface of the mass member  216   w   3  are parallel to each other in a state in which the mass member  216   w   3  is in contact with the lower surface of the lower-limit stopper  220 . Accordingly, in the key depression state, the tilt angle (rocking angle) of the hammer  216   w  is the same for all hammers  216   w . When the tilt angle of the hammer  216   w  in the key depression state is defined as a reference, the tilt angle of the hammer  216   w  on the high-pitched side is smaller than the tilt angle of the hammer  216   w  on the low-pitched side in the key release state. Accordingly, in the key release state, the engagement portion Pw 21  between the hammer  216   w  on the high-pitched side and the drive portion  211   w   1  is located to be lower than the engagement portion Pw 21  between the hammer  216   w  on the low-pitched side and the drive portion  211   w   1 . 
     As described above, the white key  211   w  tilts such that the back end is lower than the front end during the key release. The length of the drive portion  211   w   1  in the vertical direction is the same for all white keys  211   w . The height of the pivot center is the same for all white keys  211   w . Accordingly, if the position of the engagement portion Pw 21  in the vertical direction is the same during the key release, the front end of the white key  211   w  having the shorter length in the longitudinal direction might become high. In view of this, in the present embodiment, the position of the upper-limit stopper  221  in the longitudinal direction is set according to the length of the white key  211   w  in order to set the tilt angle of each hammer  216   w  in the key release state (see  FIG. 17 ). With this structure, the engagement portion Pw 21  of the white key  211   w  on the high-pitched side is located to be lower than the engagement portion Pw 21  of the white key  211   w  on the low-pitched side, whereby the height of the front ends of all white keys  211   w  is adjusted to be the same. 
     The contact point between the hammer  216   b  on the high-pitched side ( FIG. 14 ) and the upper-limit stopper  221  is located forward than the contact point between the hammer  216   b  on the low-pitched side from the hammer on the high-pitched side ( FIG. 13 ) and the upper-limit stopper  221 . In the key release state, the rear side on the lower surface of the mass member  216   b   3  is located to be lower than the front side. Therefore, the rear end of the hammer  216   b  on the high-pitched side in  FIG. 14  is located to be lower than the rear end of the hammer  216   b  on the low-pitched side in  FIG. 13 . As described above, the top surface of the mass member  216   b   3  is parallel to the lower surface of the top plate  212   a  in the key depression state. Specifically, in the state in which the mass member  216   b   3  is in contact with the lower surface of the lower-limit stopper  220 , the lower surface of the lower-limit stopper  220  and the top surface of the mass member  216   b   3  are parallel to each other. Accordingly, in the key depression state, the tilt angle (rocking angle) of the hammer  216   b  is the same for all hammers  216   b . When the tilt angle of the hammer  216   b  in the key depression state is defined as a reference, the tilt angle of the hammer  216   b  on the high-pitched side is larger than the tilt angle of the hammer  216   b  on the low-pitched side in the key release state. Consequently, in the key release state, the engagement portion Pb 21  between the hammer  216   b  on the high-pitched side and the drive portion  211   b   1  is located to be higher than the engagement portion Pb 21  between the hammer  216   b  on the high-pitched side and the drive portion  211   b   1 . 
     As described above, the black key  211   b  tilts such that the back end is lower than the front end during the key release. The length of the drive portion  211   b   1  in the vertical direction is the same for all black keys  211   b . The height of the pivot center is the same for all black keys  211   b . Accordingly, if the position of the engagement portion Pb 21  in the vertical direction is the same during the key release, the front end of the black key  211   b  having the shorter length in the longitudinal direction might become low. In view of this, in the present embodiment, the position of the upper-limit stopper  221  in the longitudinal direction is set according to the length of the black key  211   b  in order to set the tilt angle of each hammer  216   b  in the key release state (see  FIG. 18 ). With this structure, the engagement portion Pb 21  of the black key  211   b  on the high-pitched side is located to be higher than the engagement portion Pb 21  of the black key  211   b  on the low-pitched side, whereby the height of the front ends of all black keys  211   b  is adjusted to be the same. 
     In a state in which two adjacent white keys  211   w  and the black key  211   b  between the two adjacent white keys  211   w  are released, the rocking angle of each hammer is set such that the edge line R 2  of the black key  211   b  is located below the top face of one on the low-pitched side of the two white keys  211   w , and above the top face of one on the high-pitched side of the two white keys  211   w.    
     The rocking angle of each hammer is set such that, in the state in which the white key  211   w  and the black key  211   b  adjacent to the white key  211   w  are depressed respectively by the same depression force, and their rocking movement is restricted, the edge line R 2  of the black key  211   b  is located below the top face of the white key  211   w . The buffer member  220   b  and the buffer member  221   b  have elasticity. Therefore, when the key is depressed more after the hammer is brought into contact with the buffer member during the key depression, the buffer member is elastically deformed, so that the front end of the key slightly displaces downward. 
     A switch drive portion AC 21  is provided on the lower surface of each of the white key  211   w  and the black key  211   b  on the middle part. The switch drive portion AC 21  is a plate-like member extending in the vertical direction in each of the white key  211   w  and the black key  211   b , and the lower end surface of the switch drive portion AC 21  is brought into contact with the upper surface of a switch SW 21 . The switch SW 21  is provided for each key. The switch SW 21  is pressed by the corresponding key to detect whether the corresponding key is depressed or released. Specifically, when the switch SW 21  is depressed by the key, a rubber main body is deformed to make two contacts, which are formed on a circuit board  223 , short-circuit, thereby being turned ON. The circuit board  223  extends in the lateral direction. Through-holes penetrating from the upper surface to the lower surface are formed on the circuit board  223 . The through-holes correspond to a bosses  224  formed integral with the upper surface of the top plate  212   a . When screws are threaded to the bosses  224  through the through-holes, the circuit board  223  is fixed to the key frame  212 . The main bodies of the plural switches SW 21 , each corresponding to each key, are arranged on the upper surface of the circuit board  223  in the lateral direction. The position of the switch SW 21  for the white key  211   w  and the position of the switch SW 21  for the black key  211   b  in the longitudinal direction are the same. A distance Lw 23  from the front end of the white key  211   w  to the switch SW 21  in the longitudinal direction is within 30% of the distance Lw 22  from the front end of the white key  211   w  with the highest pitch to the through-hole Kw 2 , and a distance Lb 23  from the front end of the apparent portion of the black key  211   b  to the switch SW 21  is within 30% of the distance Lb 22  from the front end of the apparent portion of the black key  211   b  with the highest pitch to the through-hole Kb 2 . The switch SW 21  for the white key  211   w  and the switch SW 21  for the black key  211   b  may be arranged side by side in the lateral direction, and the positions of both switches in the longitudinal direction may be shifted. 
     A key guide  225   w  for guiding the rocking movement of the white key  211   w  is formed to project upward from the top end surface of the front plate  212   d . The key guide  225   w  is inserted into the white key  211   w  from below, and during the key depression and key release, the side face of the key guide  125   w  and the inside face of the sidewall of the white key  211   w  are in sliding contact with each other. This structure can prevent a slight displacement of the white key  211   w  in the lateral direction during the key depression and key release. 
     A key guide  225   b  for guiding the rocking movement of the black key  211   b  is formed to project upward from the upper surface of the top plate  212   a  at the front end. The key guide  225   b  is inserted into the black key  211   b  from below, and during the key depression and key release, the side face of the key guide  225   b  and the inside face of the sidewall of the black key  211   b  are in sliding contact with each other. This structure can prevent a slight displacement of the black key  211   b  in the lateral direction during the key depression and key release. 
     In the keyboard device having the configuration described above, the height of the front ends of the keys during the key release is adjusted to be the same, whereby the appearance of the key board device can be made similar to the appearance of the keyboard device for an acoustic piano during the key release. In addition, the keyboard device according to the present embodiment has high productivity, compared to the keyboard device for an acoustic piano in which the height of the front ends of the keys is adjusted to be the same by adjusting the number or the thickness of the spacer, which is sandwiched between the key support portion and the frame. 
     The distance from the top face of the apparent portion of the white key  221   w  to the pivot center is the same for all white keys  221   w , and the distance from the top face of the body of the black key  221   b  to the pivot center is the same for all black keys  221   b . Accordingly, when the through-holes Kw 2  and Kb 2  are formed in a different process after a process of molding the outer shape of the white key  221   w  and the black key  221   b , the different process can commonly be carried out for all keys to enhance productivity of the keys. The positions of the projections  213   w   1  and  213   b   1  of the key support portions  213   w  and  213   b  in the vertical direction are set to be the same for all key support portions  213   w  and  213   b , resulting in that the frame  212  that supports the keys is easily designed. In addition, the frame  212  is easily processed, and the precision can be enhanced. 
     In the planar view, the upper-limit stopper  221  is arranged to tilt, and the tilting direction of the lower surface of the mass member  216   w   3  and the tilting direction of the lower surface of the mass member  216   b   3  are set to be reverse to each other. With this structure, as for the hammers  216   w  for the white keys  211   w , the tilt angle in the key release state becomes gradually small from the hammer  216   w  on the low-pitched side toward the hammer  216   w  on the high-pitched side. As for the hammers  216   b  for the black keys  211   b , the tilt angle in the key release state becomes gradually large from the hammer  216   b  on the low-pitched side toward the hammer  216   b  on the high-pitched side. Accordingly, there is no need to provide the upper-limit stopper  221  for each hammer, whereby the number of components can be reduced, and the cost for the keyboard device can be reduced. In addition, the productivity of the keyboard device can be enhanced. 
     Upon embodying the present invention, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention. 
     In the present embodiment, the upper-limit stopper  221  tilts such that the portion on the high-pitched side is located to be forward from the portion on the low-pitched side in the planar view of the key frame  212 . However, instead of this structure, an upper-limit stopper  221 A may extend parallel to the arrangement direction of the keys as illustrated in  FIGS. 19 to 23 . In this case, a buffer member  221   c  is used instead of the buffer member  221   b . The thickness of the buffer member  221   c  in the vertical direction is different for each hammer. Specifically, the buffer member  221   c  of the hammer  216   w  for the white key  221   w  ( FIG. 20 ) on the low-pitched side is thin, while the buffer member  221   c  of the hammer  216   w  for the white key  221   w  on the high pitched side is thicker than the low-pitched side. As described above, the tilt angle of each hammer in the key release state may be set by setting the thickness of the buffer member  221   c  according to the length of the white key  221   w . Even with this structure, the height of the front ends of the white keys  211   w  in the key release state can be adjusted to be the same. The buffer member  221   c  for the black key  211   b  ( FIG. 22 ) on the low-pitched side is thick, while the buffer member  221   c  for the black key  221   b  ( FIG. 23 ) on the high-pitched side is thinner than the low-pitched side. As described above, the tilt angle of each hammer in the key release state may be set by setting the thickness of the buffer member  221   b  according to the length of the black key  221   b . Even with this structure, the height of the front ends of the black keys  211   b  in the key release state can be adjusted to be the same. 
     As illustrated in  FIGS. 24 and 25 , the lower surface of the mass member  216   w   3  and the lower surface of the mass member  216   b   3  may be parallel to the top surface of the frame FR 2  in the key release state. In this case, the thickness of the buffer member  221   b  is the same for all hammers. Therefore, the tilt angles of the hammer  216   w  and the hammer  216   b  in the key release state are the same, regardless of the assigned pitch. In view of this, as illustrated in  FIG. 26 , a spacer SP having a thickness according to the length of each key is provided on the leg portions Fw 21  and Fw 22  of the hammer  216   w  and the leg portions Fb 21  and Fb 22  of the hammer  216   b . Specifically, the spacer SP for the hammer  216   w  on the high-pitched side is set to be thin, and the spacer SP for the hammer  216   w  on the low-pitched side is set to be thicker than the high-pitched side, whereby the engagement portion Pw 21  of the white key  211   w  on the high-pitched side is located to be lower than the engagement portion Pw 21  of the white key  211   w  on the low-pitched side. Thus, the height of the front end of the white key  211   w  can be adjusted to be the same. The spacer SP for the hammer  216   b  on the high-pitched side is set to be thick, and the spacer SP for the hammer  216   b  on the low-pitched side is set to be thinner than the high-pitched side, whereby the engagement portion Pb 21  of the black key  211   b  on the high-pitched side is located to be higher than the engagement portion Pb 21  of the black key  211   b  on the low-pitched side. Thus, the height of the front end of the black key  211   b  can be adjusted to be the same. The thickness of the shock absorbing member fitted to the lower end wall of the drive portion  211   w   1  and the drive portion  211   b   1  is adjusted according to the thickness of the spacer SP. 
     In the keyboard device illustrated in  FIGS. 24 and 25 , the height of the engagement portion Pw 21  and the engagement portion Pb 21  may be adjusted by bending the connection rod  216   w   2  of the hammer  216   w  and the connection rod  216   b   2  of the hammer  216   b  on the middle portion in the longitudinal direction, not by mounting the spacer illustrated in  FIG. 26 . For example, the connection rod may be bent such that the back end of the hammer  216   w  is lifted upward, and the back end of the hammer  216   b  is pushed downward. The bending amount (bending angle) of the connection rod may be set according to the length of the engaged key. In this case, the engagement portion Pw 21  of the white key  211   w  on the high-pitched side is located to be lower than the engagement portion Pw 21  of the white key  211   w  on the low-pitched side by the structure in which the bending amount of the connection rod  216   w   2  of the hammer  216   w  on the low-pitched side increases, and the bending amount of the connection rod  216   w   2  of the hammer  216   w  on the high-pitched side decreases. With this structure, the height of the front ends of the white keys  211   w  in the key release state can be adjusted to be the same. The engagement portion Pb 21  of the black key  211   b  on the low-pitched side is located to be lower than the engagement portion Pb 21  of the black key  211   b  on the high-pitched side by the structure in which the bending amount of the connection rod  216   b   2  of the hammer  216   b  on the low-pitched side increases, and the bending amount of the connection rod  216   b   2  of the hammer  216   b  on the high-pitched side decreases. With this structure, the height of the front ends of the black keys  211   b  in the key release state can be adjusted to be the same. 
     In the embodiment described above, the white key  211   w  and the black key  211   b  are supported by the key support portions  213   w  and  213   b  of the key frame  212  by fitting the projections  213   w   1  and  213   b   1  to the through-holes Kw and Kb respectively so that the front ends of the white key  211   w  and the black key  211   b  can rock in the vertical direction. However, the white key  211   w  and the black key  211   b  can be mounted on the key frame  212  by using various supporting mechanisms, if the white key  211   w  and the black key  211   b  are supported by the key frame  212  so that the front ends of the white key  211   w  and the black key  211   b  can rock in vertical direction. For example, the rear ends of plural keys (the white key  211   w  and/or the black key  211   b ) may be are supported by the key frame  212  through elastic deformation members so that the front ends of the plural keys can rock in vertical direction. Concretely, the rear ends of the plural keys are connected to a fixing member fixed to the key frame  212  through thin and elastic connection members, wherein the fixing member is extended in the lateral direction, the connection members are extended horizontally or vertically, and the plural keys, the connection members and the fixing member are formed integrally. In this case, for example, the connection members for the white keys  211   w  are extended horizontally, and the connection members for the black keys  111   b  are extended vertically. 
     Subsequently, a third embodiment of the present invention will be described below with reference to the drawings. In the description below, a side close to a performer is defined as a “front side”, while a side far from the performer is defined as a “rear side”. A high-pitched side is defined as a “right side”, while a low-pitched side is defined as a “left side”. 
     A keyboard device includes plural white keys  311   w  and plural black keys  311   b  as illustrated in  FIG. 27 . A different pitch is assigned to each of plural white keys  311   w  and each of plural black keys  311   b . In the present embodiment, one of “C 3 ”, “D 3 ”, . . . “C 6 ” is assigned to the white keys  311   w , while one of “C# 3 ”, “D# 3 ”, “B# 5 ” is assigned to the black keys  311   b . The white keys  311   w  and black keys  311   b  are integrally formed to have a long shape by a synthetic resin. The white keys  311   w  are configured such that the length thereof is gradually shorter toward the white key  311   w  on the high-pitched side from the white key  311   w  on the low-pitched side. The black keys  311   b  are configured such that the length thereof is gradually shorter toward the black key  311   b  on the high-pitched side from the black key  311   b  on the low-pitched side. The back end of the black key  311   b  is located posterior to the back end of the adjacent white key  311   w.    
     As illustrated in  FIGS. 28 to 31 , each of the white keys  311   w  has a width in the vertical direction smaller than that of the black key  311   b , and has a width in the lateral direction larger than that of the black key  311   b . The white key  311   w  and the black key  311   b  have a hollow shape including a thin top wall extending in the longitudinal direction, and thin sidewalls extending downward from left and right ends of the top wall respectively, with no bottom. 
     Through-holes Kw 3  and Kb 3  that are opposite to each other are formed on the rear part of the sidewall of the white key  311   w  and the black key  311   b . The distance from the through-holes Kw 3  and Kb 3  to the back end of each key is the same for all keys. The white key  311   w  and the black key  311   b  are supported by a key support portion  313   w  and a key support portion  313   b  of a later-described key frame  312  with the through-holes Kw 3  and Kb 3 . In the key release state, the white key  311   w  and the black key  311  tilt such that the back end becomes lower than the front end. The back end of the white key  311   w  goes into a casing of the electronic musical instrument, when the keyboard device is assembled to the electronic musical instrument. The portion of the white key anterior to the portion going into the casing is referred to as an apparent portion of the white key  311   w . An edge line is formed on the portion where the side face and the top face of the white key  311   w  cross each other. The black key  311   b  has a portion projecting upward from the top face of the white key  311   w  in a state in which the black key  311   b  is not depressed, and the adjacent white keys  311   w  are not depressed. The projecting portion is referred to as an apparent portion of the black key  311   b . The portion lower than the apparent portion of the black key  311   b  is referred to as a body. A performer depresses or releases the apparent portions of the white key  311   w  and the black key  311   b . Specifically, the apparent portion corresponds to an operation portion in the present invention. The width of the apparent portion of the black key  311   b  in the lateral direction becomes narrower toward the top end, and the width of the body in the lateral direction is the same. Specifically, the side face of the apparent portion tilts inward with respect to the side face of the body. An edge line R 3  is formed on the boundary between the apparent portion of the black key  311   b  and the body (see  FIGS. 30 and 31 ). 
     The key frame  312  has a top plate  312   a  extending in the longitudinal direction and lateral direction. The position of the front end of the top plate  312   a  at the low-pitched side and the position of the front end at the high-pitched side are the same, but the back end at the low-pitched side is located posterior to the back end at the high-pitched side. The key frame  312  also has a front plate  312   b  vertically extending downward from the front end of the top plate  312   a , a bottom plate  312   c  horizontally extending from the lower end of the front plate  312   b , and a front plate  312   d  vertically extending upward from the front end of the bottom plate  312   c . The key frame  312  also includes a rear plate  312   e  vertically extending downward from the back end of the top plate  312   a , and a bottom plate  312   f  horizontally extending rearward from the lower end of the rear plate  312   e . The height of the lower surface of the bottom plate  312   c  and the height of the lower surface of the bottom plate  312   f  are the same. The keyboard device is supported by a frame FR 3  of an electronic musical instrument by the structure in which the lower surface of the bottom plate  312   c  and the lower surface of the bottom plate  312   f  are brought into contact with the frame FR 3  of the electronic musical instrument and fixed thereto. The above-described key support portion  313   w  and the key support portion  313   b  are formed to project upward from the upper surface of the top plate  312   a . The key support portion  313   b  is located posterior to the adjacent key support portion  313   w . The key support portion  313   w  and the key support portion  313   b  respectively include two opposing plates, and a projection  313   w   1  and projection  313   b   1  that project inward. The projections  313   w   1  and  313   b   1  are fitted to the through-holes Kw 3  and Kb 3  respectively. Therefore, the white key  311   w  and the black key  311   b  are supported to be rotatable about the projections  313   w   1  and  313   b   1 , and their front ends can rock in the vertical direction with the through-holes Kw 3  and Kb 3  and the center axes of the projections  313   w   1  and the projections  313   b   1  being defined as a pivot center. The position of the projection  313   w   1  and the position of the projection  313   b   1  in the vertical direction are the same for all key support portions. Specifically, the height of the pivot center is the same for all keys. The distance between the top face of the apparent portion of the white key  311   w  (i.e., the plane including the right and left edge lines of the white key  311   w ) and its pivot center in the vertical direction is the same for all white keys  311   w . The distance between the top face of the operation portion of the black key  311   b  (i.e., the plane including the right and left edge lines R 3  of the black key  311   b ) and its pivot center in the vertical direction is the same for all black keys  311   b.    
     A drive portion  311   w   1  extends downward from the middle portion of the apparent portion of the white key  311   w . The drive portion  311   w   1  has a hollow shape including a thin front wall extending in the vertical direction, and thin sidewalls extending rearward from left and right ends of the front wall, with no rear wall. The lower end of the drive portion  311   w   1  is closed by a lower end wall. The length of the drive portion  311   w   1  in the vertical direction is different according to the assigned pitch. The length of the drive portion  311   w   1  in the vertical direction will be described later. On the other hand, the black key  311   b  also has a drive portion  311   b   1  same as the drive portion  311   w   1  of the white key  311   w . The drive portion  311   b   1  has a connection portion that extends downward from the front end of the apparent portion of the black key  311   b  and that is slightly curved to the front, and a vertical portion projecting downward from the leading end of the connection portion. The configuration of the vertical portion is the same for the drive portion  311   w   1 . The length of the drive portion  311   b   1  in the vertical direction is different according to the assigned pitch. The length of the drive portion  311   b   1  in the vertical direction will be described later. 
     A distance Lw 31  from the front end of the white key  311   w  to the drive portion  311   w   1  in the longitudinal direction is within 30% of a distance Lw 32  from the front end of the white key  311   w  with the highest pitch (i.e., the shortest key of the plural white keys  311   w ) to the through-hole Kw 3 . The distance Lw 31  is the same for all white keys  311   w . A distance Lb 31  from the front end of the apparent portion of the black key  311   b  to the drive portion  311   b   1  in the longitudinal direction is within 30% of a distance Lb 32  from the front end of the apparent portion of the black key  311   b  with the highest pitch (e.g., the shortest key of the plural black keys  311   b ) to the through-hole Kb 3 . The distance Lb 31  is the same for all black keys  311   b . The position of the drive portion  311   w   1  and the position of the drive portion  311   b   1  in the longitudinal direction in the key-released state of the white key  311   w  and the black key  311   b  are the same. Specifically, the drive portions  311   w   1  and the drive portions  311   b   1  are located anterior to the front end of the apparent portion of the black keys  311   b , and the drive portions  311   w   1  and the drive portions  311   b   1  are arranged in the lateral direction. 
     The lower ends of the drive portion  311   w   1  and the drive portion  311   b   1  are respectively engaged with front ends of hammers  316   w  and  316   b  in the opening formed between the front plate  312   b  and the front plate  312   d . As described in detail later, the hammer  316   w  and the hammer  316   b  rock with the rocking movement of the corresponding white key  311   w  and the black key  311   b  with which the respective hammers  316   w  and  316   b  are engaged. 
     The hammer  316   w  includes a base  316   w   1  made of synthetic resin, a connection rod  316   w   2  made of metal, and a mass member  316   w   3 . Like the hammer  316   w , the hammer  316   b  includes a base  316   b   1 , a connection rod  316   b   2 , and a mass member  316   b   3 . The base  316   w   1  and the base  316   b   1  are plate-like members, and formed with through-holes Hw 3  and Hb 3 , respectively, from the right side face to the left side face. A hammer support portion  318   w  and a hammer support portion  318   b  are formed to project downward from the lower surface of the top plate  312   a . The hammer support portions  318   w  and  318   b  are formed to have two opposing plates, and respectively have projections  318   w   1  and  318   b   1  projecting inward. The projections  318   w   1  and  318   b   1  are respectively fitted to the through-holes Hw 3  and Hb 3 . With this structure, the bases  316   w   1  and  316   b   1  are supported to be rotatable about the projections  318   w   1  and  318   b   1 . Specifically, the hammer  316   w  and the hammer  316   b  are supported such that the front ends and the back ends can be rocked in the vertical direction. The positions of the hammer support portion  318   w  and the hammer support portion  318   b  in the longitudinal direction and in the vertical direction are the same for all hammer support portions  318   w  and  318   b . Specifically, plural hammer support portions  318   w  and the plural hammer support portions  318   b  are arranged side by side in the lateral direction, and the positions of the pivot centers of all hammers  316   w  and hammers  316   b  in the longitudinal direction and in the vertical direction are the same for all hammers  316   w  and  316   b . In other words, the pivot centers of the hammers  316   w  and the hammers  316   b  are located on the same straight line extending in the lateral direction. 
     The base  316   w   1  includes a pair of leg portion Fw 31  and leg portion Fw 32  on its front end. The upper leg portion Fw 31  is formed to be shorter than the lower leg portion Fw 32 . Like the base  316   w   1 , the base  316   b   1  includes a pair of leg portion Fb 31  and leg portion Fb 32  on its front end. An elongated slit-like opening  312   b   1  extending in the vertical direction is formed on the front plate  312   b  for each of the hammers  316   w  and  316   b . The front end of each hammer  316   w  and the front end of each hammer  316   b  project forward of the front plate  312   b  through the opening  312   b   1 . The wall of the lower end of the drive portion  311   w   1  enters between the leg portions Fw 31  and Fw 32 , while the wall of the lower end of the drive portion  311   b   1  enters between the leg portions Fb 31  and Fb 32 . Specifically, the leg portions Fw 31  and Fb 31  enter between the walls of the lower ends of the drive portions  311   w   1  and  311   b   1  and intermediate walls that form gaps with the walls of the lower ends in the drive portions  311   w   1  and  311   b   1 . A shock absorbing member SA such as rubber, urethane, or felt is fitted and fixed on the wall of the lower end of each of the drive portions  311   w   1  and  311   b   1 . The shock absorbing member SA attenuates shock caused by the collision between the lower end of the drive portion  311   w   1  and the upper surface of the leg portion Fw 32 , the collision between the lower end of the drive portion  311   b   1  and the upper surface of the leg portion Fb 32 , the collision between the lower end of the drive portion  311   w   1  and the lower surface of the leg portion Fw 31 , and the collision between the lower end of the drive portion  311   b   1  and the lower surface of the leg portion Fb 31 . 
     The front end of the connection rod  316   w   2  and the front end of the connection rod  316   b   2  are assembled to the back end of the base  316   w   1  and the back end of the base  316   b   1 , respectively. The connection rods  316   w   2  and  316   b   2  extend rearward. The position of the back end of the connection rod  316   w   2  and the position of the back end of the connection rod  316   b   2  in the longitudinal direction are the same. The mass member  316   w   3  and the mass member  316   b   3 , described later, are assembled to the back end of the connection rod  316   w   2  and the back end of the connection rod  316   b   2 , respectively. 
     The mass member  316   w   3  and the mass member  316   b   3  are formed to have a plate-like shape. The mass member  316   w   3  and the mass member  316   b   3  are long in the longitudinal direction. The mass member  316   w   3  and the mass member  316   b   3  are assembled to the connection rods  316   w   2  and  316   b   2  in such a manner that the thickness thereof is along the lateral direction. 
     As described above, the position of the pivot point of the key is different depending upon the assigned pitch. Therefore, the distance from the pivot center of the white key  311   w  to an engagement portion Pw 31  where the leg portion Fw 32  and the drive portion  311   w   1  are engaged with each other (brought into contact with each other) is different depending upon the assigned pitch. The distance from the pivot center of the black key  311   b  to an engagement portion Pb 31  where the leg portion Fb 32  and the drive portion  311   b   1  are engaged with each other (brought into contact with each other) is also different depending upon the assigned pitch. A key depression/release operation position W 30  of the white key  311   w  that is the front end of the position of the white key  311   w  with the potentiality of being depressed or released is located anterior to the engagement portion Pw 31 , while a key depression/release operation position B 30  of the black key  311   b  that is the front end of the position of the black key  311   b  with the potentiality of being depressed or released is located posterior to the engagement portion Pb 31 . Therefore, if the masses of the mass members for all hammers are equal, a key touch feeling is heavier on the middle-pitched part than on the low-pitched part, and the key touch feeling is heavier on the high-pitched part than on the middle-pitched part, on the key depression/release operation positions W 30  and B 30 , because of the principle of leverage. 
     In addition, in this case, the key touch feeling of the white keys  311   w  and the black keys  311   b  in each range is not equal. Specifically, the key touch feeling of the black key  311   b  is heavier than the key touch feeling of the adjacent two white keys  311   w . In view of this, the mass of the mass member  316   w   3  and the mass of the mass member  316   b   3  are adjusted for each key as illustrated in  FIG. 32 . Specifically, as illustrated in a characteristic curve indicating the masses of the mass members  316   w   3  and  316   b   3  in the order of pitches, the masses of the mass members  316   w   3  and  316   b   3  are adjusted such that the characteristic curve of the mass member  316   w   3  and the characteristic curve of the mass member  316   b   3  are parallel downward-sloping curves, wherein the characteristic curve of the mass member  316   b   3  is located below the characteristic curve of the mass member  316   w   3 . Thus, as illustrated by a chain line in  FIG. 33 , the key touch feeling on the key depression/release operation positions W 30  and B 30  becomes gradually lighter toward the high-pitched side from the low-pitched side. Therefore, as illustrated by a broken line in  FIG. 33 , the key touch feeling on key depression/release operation positions W 31  and B 31  located posterior to the key depression/release operation positions W 30  and B 30  by a distance d 3  also becomes gradually lighter toward the high-pitched side from the low-pitched side. Since the length of the key to which a higher pitch is assigned is shorter, the difference between the key touch feeling on the key depression/release operation positions W 30  and B 30  and the key touch feeling on the key depression/release operation positions W 31  and B 31  becomes larger toward the high-pitched side from the low-pitched side. Specifically, the difference in the key touch feeling caused by the longitudinal difference of the key depression/release operation position is small on the low-pitched side, moderate in the middle-pitched side, and large on the high-pitched side. 
     When the white key  311   w  and the black key  311   b  are released, the front ends of the hammers  316   w  and  316   b  displace upward due to their own weight of the hammers  316   w  and  316   b . In this case, the drive portion  311   w   1  and the drive portion  311   b   1  are biased upward by the leg portion Fw 32  and the leg portion Fb 32  respectively, whereby the front ends of the white key  311   w  and the black key  311   b  displace upward. On the other hand, when the white key  311   w  and the black key  311   b  are depressed, the lower surfaces of the drive portion  311   w   1  and the drive portion  311   b   1  press the upper surfaces of the leg portion Fw 32  and the leg portion Fb 32  respectively, whereby the front ends of the hammer  316   w  and the hammer  316   b  respectively displace downward. 
     A lower-limit stopper  320  is provided to the key frame  312 . During the key depression, the lower-limit stopper  320  is brought into contact with the upper surfaces of the mass member  316   w   3  and the mass member  316   b   3  of the hammer  316   w  and the hammer  316   b  so as to restrict the upward displacement of the back ends of the hammer  316   w  and the hammer  316   b , thereby restricting the downward displacement of the front ends of the white key  311   w  and the black key  311   b . The lower-limit stopper  320  includes a stopper rail  320   a  and a buffer member  320   b . The stopper rail  320   a  protrudes downward from the lower surface at the middle of the top plate  312   a . The stopper rail  320   a  extends parallel to the lateral direction. The projection amount of the stopper rail  320   a  from the lower surface of the top plate  312   a  on the contact portion between the stopper rail  320   a  and each hammer is constant in the lateral direction. The buffer member  320   b  is fixed to the lower end surface of the stopper rail  320   a . The buffer member  320   b  is a long member made of a shock-absorbing member such as rubber or felt. The sectional shape of the buffer member  320   b  is uniform from one end to the other end. 
     An upper-limit stopper  321  is provided to the middle portion of the frame FR 3 . During the key release, the upper-limit stopper  321  is brought into contact with the lower surfaces of the mass member  316   w   1  and the mass member  316   b   1  of the hammer  316   w  and the hammer  316   b  so as to restrict the downward displacement of the back ends of the hammer  316   w  and the hammer  316   b , thereby restricting the upward displacement of the front ends of the white key  311   w  and the black key  311   b . Like the lower-limit stopper  320 , the upper-limit stopper  321  includes a stopper rail  321   a  and a buffer member  321   b . Specifically, in a planar view of the key frame  312 , the stopper rail  320   a  extends in parallel in the lateral direction. The projection amount from the frame FR 3  is constant in the lateral direction. The buffer member  321   b  is fixed on the upper surface of the stopper rail  321   a . Like the buffer member  320   b , the sectional shape of the buffer member  321   b  is uniform from one end to the other end. The stopper rail  320   a  and the stopper rail  321   a  may continuously extend in the lateral direction, or may discontinuously extend. The stopper rail  320   a  and the stopper rail  321   a  may be formed integral with the top plate  312   a  and the frame FR 3  respectively, or may be formed as separate components and assembled to the top plate  312   a  and the frame FR 3  respectively. 
     As described above, the white key  311   w  tilts such that the back end is lower than the front end during the key release. The height of the pivot center of the white key  311   w  is the same for all white keys  311   w . The position of the engagement portions Pw 31  of two different white keys  311   w  in the vertical direction are the same during the key release. Accordingly, if the length of the drive portion  311   w   1  of the white key  311   w  in the vertical direction is the same for all white keys  311   w , the front end of the white key  311   w  having the shorter length in the longitudinal direction might become high. In view of this, in the present embodiment, the length of the drive portion  311   w   1  in the vertical direction is set according to the length of the white key  311   w  in order to set the height of the front end of each white key  311   w  in the key release state to be the same. Specifically, the length of the drive portion  311   w   1  in the vertical direction for the white key  311   w  having the shorter length in the longitudinal direction is set to be small (see  FIG. 34 ). As described above, in the present embodiment, the size of the white key  311   w  in the vertical direction is set according to the longitudinal distance from the front end of the white key  311   w  to the key support portion  313   w  (the axis of the projection  313   w   1 ). 
     As described above, the black key  311   b  tilts such that the back end is lower than the front end during the key release. The height of the pivot center of the black key  311   b  is the same for all black keys  311   b . The position of the engagement portions Pb 31  of two different black keys  311   b  in the vertical direction are the same during the key release. Accordingly, if the length of the drive portion  311   b   1  of the black key  311   b  in the vertical direction is the same for all black keys  311   b , the front end of the black key  311   b  having the shorter length in the longitudinal direction might become high. In view of this, in the present embodiment, the length of the drive portion  311   b   1  in the vertical direction is set according to the length of the black key  311   b  in order to set the height of the front end of each black key  311   b  in the key release state to be the same. Specifically, the length of the drive portion  311   b   1  in the vertical direction for the black key  311   b  having the shorter length in the longitudinal direction is set to be long (see  FIG. 35 ). As described above, in the present embodiment, the size of the black key  311   b  in the vertical direction is set according to the longitudinal distance from the front end of the black key  311   b  to the key support portion  313   b  (the axis of the projection  313   b   1 ). 
     In a state in which two adjacent white keys  311   w  and the black key  311   b  between the two adjacent white keys  311   w  are released, the rocking angle of each hammer is set such that the edge line R 3  of the black key  311   b  is located below the top face of one on the low-pitched side of the two white keys  311   w , and above the top face of one on the high-pitched side of the two white keys  311   w.    
     The tilt angle of each key is set such that, in the state in which the white key  311   w  and the black key  311   b  adjacent to the white key  311   w  are depressed respectively by the same depression force, and their rocking movement is restricted, the edge line R 3  of the black key  311   b  is located below the top face of the white key  311   w . The buffer member  320   b  and the buffer member  321   b  have elasticity. Therefore, when the key is depressed more after the hammer is brought into contact with the buffer member during the key depression, the buffer member is elastically deformed, so that the front end of the key slightly displaces downward. 
     A switch drive portion AC 31  is provided on the lower surface of each of the white key  311   w  and the black key  311   b  on the middle part. The switch drive portion AC 31  is a plate-like member extending in the vertical direction in each of the white key  311   w  and the black key  311   b , and the lower end surface of the switch drive portion AC 31  is brought into contact with the upper surface of a switch SW 31 . The switch SW 31  is provided for each key. The switch SW 31  is pressed by the corresponding key to detect whether the corresponding key is depressed or released. Specifically, when the switch SW 31  is depressed by the key, a rubber main body is deformed to make two contacts, which are formed on a circuit board  323 , short-circuit, thereby being turned ON. The circuit board  323  extends in the lateral direction. Through-holes penetrating from the upper surface to the lower surface are formed on the circuit board  323 . The through-holes correspond to a bosses  324  formed integral with the upper surface of the top plate  312   a . When screws are threaded to the bosses  324  through the through-hole, the circuit board  323  is fixed to the key frame  312 . The main bodies of the plural switches SW 31 , each corresponding to each key, are arranged on the upper surface of the circuit board  323  in the lateral direction. The position of the switch SW 31  for the white key  311   w  and the position of the switch SW 31  for the black key  311   b  in the longitudinal direction are the same. A distance Lw 33  from the front end of the white key  311   w  to the switch SW 31  in the longitudinal direction is within 30% of the distance Lw 32  from the front end of the white key  311   w  with the highest pitch to the through-hole Kw 3 , and a distance Lb 33  from the front end of the apparent portion of the black key  311   b  to the switch SW 31  is within 30% of the distance Lb 32  from the front end of the apparent portion of the black key  311   b  with the highest pitch to the through-hole Kb 3 . The switch SW 31  for the white key  311   w  and the switch SW 31  for the black key  311   b  may be arranged side by side in the lateral direction, and the positions of both switches in the longitudinal direction may be shifted. 
     A key guide  325   w  for guiding the rocking movement of the white key  311   w  is formed to project upward from the top end surface of the front plate  312   d . The key guide  325   w  is inserted into the white key  311   w  from below, and during the key depression and key release, the side face of the key guide  325   w  and the inside face of the sidewall of the white key  311   w  are in sliding contact with each other. This structure can prevent a slight displacement of the white key  311   w  in the lateral direction during the key depression and key release. 
     A key guide  325   b  for guiding the rocking movement of the black key  311   b  is formed to project upward from the upper surface of the top plate  312   a  at the front end. The key guide  325   b  is inserted into the black key  311   b  from below, and during the key depression and key release, the side face of the key guide  325   b  and the inside face of the sidewall of the black key  311   b  are in sliding contact with each other. This structure can prevent a slight displacement of the black key  311   b  in the lateral direction during the key depression and key release. 
     In the keyboard device having the configuration described above, the size of each white key  311   w  in the vertical direction is set according to the longitudinal distance from the front end of each white key  311   w  to the key support portion  313   w  (the axis of the projection  313   w   1 ) in order that the height of the front end of each white key  311   w  during the key release is adjusted to be the same. In addition, the size of each black key  311   b  in the vertical direction is set according to the longitudinal distance from the front end of each black key  311   b  to the key support portion  313   b  (the axis of the projection  313   b   1 ) in order that the height of the front end of each black key  311   b  during the key release is adjusted to be the same. Accordingly, the appearance of the keyboard device can be made similar to the appearance of the keyboard device for an acoustic piano during the key release. In addition, the keyboard device according to the present embodiment has high productivity, because there is no need to adjust the height of the front ends of the keys to be the same by adjusting the number or the thickness of the spacer, which is sandwiched between the key support portion and the frame, as in the keyboard device such as an acoustic piano. 
     The distance from the top face of the apparent portion of the white key  311   w  to the pivot center is the same for all white keys  311   w , and the distance from the top face of the body of the black key  311   b  to the pivot center is the same for all black keys  311   b . Accordingly, when the through-holes Kw 3  and Kb 3  are formed in a different process after a process of molding the outer shape of the white key  311   w  and the black key  311   b , the different process can commonly be carried out for all keys to enhance productivity of the keys. The positions of the projections  313   w   1  and  313   b   1  of the key support portions  313   w  and  313   b  in the vertical direction are set to be the same for all key support portions  313   w  and  313   b , resulting in that the frame  312  that supports the keys is easily designed. In addition, the frame  312  is easily processed, and the precision can be enhanced. 
     Upon embodying the present invention, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the scope of the present invention. 
     According to the embodiment described above, the length of the drive portion  311   w   1  in the vertical direction for the white key  311   w  having the shorter length in the longitudinal direction is set to be short. Instead of this structure, the length of the drive portion  311   w   1  in the vertical direction may be set to be the same for all white keys  311   w , and the length of the body of each white key  311   w , in the vertical direction, excluding the drive portion  311   w   1  may be set such that the height of the front end of the white key  311   w  in the key release state becomes the same for all white keys  311   w . Specifically, the body of the white key  311   w  in the vertical direction, excluding the drive portion  311   w   1 , for the white key  311   w  having the shorter length in the longitudinal direction may be set to be short. As illustrated in  FIG. 36A , the white key  311   w  may be formed in such a manner that an upper part Uw, a middle part Mw, and a lower part Lw are combined to be superimposed in the vertical direction, and a front part Nw is assembled to a front end of the middle part Mw. The upper part Uw is formed to have a thin plate-like shape. The middle part Mw is formed to have a prism shape. The lower part Lw is formed to have a thin plate-like shape. The drive portion  311   w   1  extends downward from the lower surface of the lower part Lw. In this case, the upper part Uw and the lower part Lw may be set to be the same for all white keys  311   w , and the size Yw in the longitudinal direction and the size Zw in the vertical direction of the middle part Mw may be set according to the assigned pitch. Specifically, the vertical size Zw of the middle part Mw whose longitudinal size Yw is set to be short is set to be short. Even with this structure, the height of the front end of each white key  311   w  in the key release state can be adjusted to be the same. Since the upper part Uw and the lower part Lw are made common, cost can be reduced. In the example described above, the size Zw of the middle part Mw is set according to the size Yw. However, instead of this structure, or in addition to this structure, the size of the plate-like portion of the lower part Lw may be set according to the size Yw. 
     The black key  311   b  can be configured like the white key  311   w . Specifically, the length of the drive portion  311   b   1  in the vertical direction may be set to be the same for all black keys  311   b , and the length of the body of each black key  311   b , in the vertical direction, excluding the drive portion  311   b   1  may be set such that the height of the front end of the black key  311   b  in the key release state becomes the same for all black keys  311   b . Specifically, the body of the black key  311   b  in the vertical direction, excluding the drive portion  311   b   1 , for the black key  311   b  having the shorter length in the longitudinal direction may be set to be long. As illustrated in  FIG. 36B , the black key  311   b  may be formed in such a manner that an upper part Ub, a middle part Mb, and a lower part Lb are combined to be superimposed in the vertical direction. The upper part Ub is formed to have a prism shape in which a cross-section perpendicular to the longitudinal direction has a trapezoidal shape. The upper part Ub corresponds to the apparent portion of the black key  311   b . The middle part Mb is formed to have a prism shape. The lower part Lb is formed to have a thin plate-like shape. The drive portion  311   b   1  extends downward from the lower surface of the lower part Lb. In this case, the upper part Ub and the lower part Lb may be set to be the same for all black keys  311   b , and the size Yb in the longitudinal direction and the size Zb in the vertical direction of the middle part Mb may be set according to the assigned pitch. Specifically, the vertical size Zb of the middle part Mb whose longitudinal size Yb is set to be short is set to be long. Even with this structure, the height of the front end of each black key  311   b  in the key release state can be adjusted to be the same. Since the upper part Ub and the lower part Lb are made common, cost can be reduced. In the example described above, the size Zb of the middle part Mb is set according to the size Yb. However, instead of this structure, or in addition to this structure, the size of the plate-like portion of the lower part Lb may be set according to the size Yb. 
     The total size of the white key  311   w  in the vertical direction may be set to be the same for all white keys  311   w . In this case, a size Zsa of a portion, located below the lower end wall of the drive portion  311   w   1  and the drive portion  311   b   1 , of the shock absorbing member SA may be set in order that the height of the front end of each white key  311   w  in the key release state becomes the same for all white keys  311   w . Specifically, the size Zsa for the white key  311   w  having the shorter length in the longitudinal direction may be set to be short. The total size of the black key  311   b  in the vertical direction may be set to be the same for all black keys  311   b . In this case, the size Zsa may be set in order that the height of the front end of each black key  311   b  in the key release state becomes the same for all black keys  311   b . Specifically, the size Zsa for the black key  311   b  having the shorter length in the longitudinal direction may be set to be long. Even with this structure, the effect same as the embodiment described above can be obtained. 
     In the embodiment described above, the white key  311   w  and the black key  311   b  are supported by the key support portions  313   w  and  313   b  of the key frame  312  by fitting the projections  313   w   1  and  313   b   1  to the through-holes Kw 3  and Kb 3  respectively so that the front ends of the white key  311   w  and the black key  311   b  can rock in the vertical direction. However, the white key  311   w  and the black key  311   b  can be mounted on the key frame  312  by using various supporting mechanisms, if the white key  311   w  and the black key  311   b  are supported by the key frame  312  so that the front ends of the white key  311   w  and the black key  311   b  can rock in vertical direction. For example, the rear ends of plural keys (the white key  311   w  and/or the black key  311   b ) may be are supported by the key frame  312  through elastic deformation members so that the front ends of the plural keys can rock in vertical direction. Concretely, the rear ends of the plural keys are connected to a fixing member fixed to the key frame  312  through thin and elastic connection members, wherein the fixing member is extended in the lateral direction, the connection members are extended horizontally or vertically, and the plural keys, the connection members and the fixing member are formed integrally. In this case, for example, the connection members for the white keys  311   w  are extended horizontally, and the connection members for the black keys  311   b  are extended vertically.