Patent Publication Number: US-9424825-B2

Title: Keyboard apparatus for an electronic musical instrument

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a keyboard apparatus for an electronic musical instrument, the keyboard apparatus having reaction force generation members for generating a reaction force by elastically deforming in response to a player&#39;s operation. 
     2. Description of the Related Art 
     Conventionally, there are keyboard musical instruments such as electronic organs and electronic pianos having rubber-dome reaction force generation members for exerting reaction force against the depression of keys. For example, Japanese Unexamined Patent Publication No. 11-175067 discloses a keyboard apparatus having reaction force generation members (key switches) each having a rubber dome on a circuit board fastened to a frame which supports keys located above the frame so that the keys can pivot. The reaction force generation members of white keys and black keys are configured the same. The reaction force generation members for black keys are located behind the reaction force generation members for white keys. Furthermore, the reaction force generation members are elastically deformed by being depressed by the keys depressed by a player, so that the player can perceive the same key touch on both the white keys and the black keys. 
     SUMMARY OF THE INVENTION 
     However, the above-described conventional keyboard apparatus is configured such that the height of the reaction force generation members of the white keys is the same as the height of the reaction force generation members of the black keys, while the amount of stroke is different between the white keys and the black keys. Therefore, it is difficult for the conventional keyboard apparatus to provide the same key touch both on the white keys and the black keys. Furthermore, not only in the case of the above-described conventional apparatus but also in many cases, conventional apparatuses generally have a keyboard in which the structure is different between white keys and black keys, and more specifically, the length of each key, the amount of key-stroke, the position of an axis of the key and the like are different between the white keys and the black keys. In order to solve these problems, reaction force generation members whose size, shape, function and the like are different between white keys and black keys have to be employed. In a case where the dome-shaped reaction force generation members such as the above-described conventional art are employed, however, reaction force generation members whose size, shape, function and the like are almost the same both on white keys and black keys are required in order to provide a player with the same key touch both on the white keys and the black keys. 
     The present invention was accomplished to solve the above-described problems and to satisfy the request, and an object thereof is to provide a keyboard apparatus for an electronic musical instrument, the keyboard apparatus providing a player with almost the same key touch both on white keys and black keys. As for descriptions about respective constituent features of the present invention, furthermore, reference letters of corresponding components of embodiments described later are provided in parentheses to facilitate the understanding of the present invention. However, it should not be understood that the constituent features of the present invention are limited to the corresponding components indicated by the reference letters of the embodiments. 
     In order to achieve the above-described object, the present invention provides a keyboard apparatus for an electronic musical instrument, the keyboard apparatus including a plurality of keys composed of white keys ( 11   w ) and black keys ( 11   b ), each key pivoting about a corresponding pivot axis (Cw, Cb) so that a front end of the key can move up and down, and a plurality of reaction force generation members ( 21   w ,  21   b ) which are provided for the plurality of keys, respectively, and are made of an elastic body, and each of which is depressed by a depression of a corresponding key to generate a reaction force against the depression of the corresponding key, wherein each of the reaction force generation members has a dome portion ( 21   w   1 ,  21   b   1 ) which is thin and shaped like a dome so as to be elastically deformed by depression, and a base portion which is thick and is formed integrally with the dome portion to support the dome portion, the base portion extending downward seamlessly from all circumferences of a lower end of the dome portion to jut outward from a lower end surface of the dome portion; and a position of a point (Pw, Pw′) of intersection between the lower end surface of the dome portion of the white key and an axis line (Yw, Yb) of the dome portion of either the white key or the black key is displaced from a position of a point (Pb, Pb′) of intersection between the lower end surface of the dome portion of the black key and the axis line of the dome portion of the either key. 
     In this case, for example, a position of a point (Pw) of intersection between the lower end surface of the dome portion of the white key and the axis line of the dome portion of the white key may be displaced in a vertical direction of the keys from a position of a point (Pb) of intersection between the lower end surface of the dome portion of the black key and the axis line of the dome portion of the black key. Furthermore, the dome portion of the white key may have the same shape and size as the dome portion of the black key. 
     According to the present invention configured as above, by displacing the position of the point of intersection between the lower end surface of the dome portion of the white key and the axis line of the dome portion of either the white key or the black key from the position of the point of intersection between the lower end surface of the dome portion of the black key and the axis line of the dome portion of the either key, the lower end surface of the dome portion of the white key is substantially displaced from the lower end surface of the dome portion of the black key. As a result, the keyboard apparatus whose reaction force generation members for the white keys have a height different from the height of the reaction force generation members for the black keys can have the dome portions configured the same or roughly the same for both the white keys and the black keys to provide a player with roughly the same key touch on the white keys and the black keys. 
     It is another feature of the present invention that the position of the point of intersection between the lower end surface of the dome portion of the white key and the axis line of the dome portion of the white key is displaced in a direction in which the white key and the black key extend from the position of the point of intersection between the lower end surface of the dome portion of the black key and the axis line of the dome portion of the black key. As a result, the keyboard apparatus in which the reaction force generation members for the white keys are located in a position different in the direction in which the white keys and the black keys extend from the reaction force generation members for the black keys can provide a player with roughly the same key touch on the white keys and the black keys. 
     It is a further feature of the present invention that the reaction force generation members of the white keys are formed integrally with the reaction force generation members of the black keys; and the base portion of the white key is shaped differently from the base portion of the black key. In this case, for example, a step ( 21   p ,  21   q ) or slope ( 21   r ) may be provided between an upper surface of the base portion of the white key and an upper surface of the base portion of the black key. Only by providing the integrally formed reaction force generation members for the white keys and the black keys at a position with varying heights, as a result, the base portions of the white keys and the black keys can absorb the difference in height between the white keys and the black keys. Therefore, the keyboard apparatus not only provides a player with roughly the same key touch both on the white keys and the black keys, but also facilitates the assembly of the reaction force generation members. 
     It is a still further feature of the present invention that the reaction force generation members of the white keys are formed integrally with the reaction force generation members of the black keys; and an undersurface of the base portion of the white key and an undersurface of the base portion of the black key are seamlessly inclined in the direction in which the white key and the black key extend. Only by providing the integrally formed reaction force generation members for the white keys and the black keys at a position with required varying heights, as a result, the inclination of the undersurface of the base portions of the white keys and the black keys can absorb the difference in height between the white keys and the black keys. Therefore, the keyboard apparatus not only provides a player with roughly the same key touch both on the white keys and the black keys, but also facilitates the assembly of the reaction force generation members. 
     Furthermore, a feature of the present invention can be also understood as providing a keyboard apparatus for an electronic musical instrument, the keyboard apparatus including a plurality of keys composed of white keys ( 11   w ) and black keys ( 11   b ), each key pivoting about a corresponding pivot axis (Cw, Cb) so that a front end of the key can move up and down, and a plurality of reaction force generation members ( 21   w ,  21   b ) which are provided for the plurality of keys, respectively, and are made of an elastic body, and each of which is depressed by a depression of a corresponding key to generate a reaction force against the depression of the corresponding key, wherein each of the reaction force generation members has a body portion ( 21   w   1 ,  21   b   1 ) which is thin so as to be elastically deformed by depression, and a base portion ( 21   w   3 ,  21   b   3 ) which is thick and is formed integrally with the body portion to support the body portion, the base portion extending downward seamlessly from all circumferences of a lower end of the body portion to jut outward from the lower end of the body portion; and the lower end of the body portion of the white key is displaced in a vertical direction from the lower end of the body portion of the black key. 
     According to the feature of the invention, the keyboard apparatus in which the reaction force generation members for the white keys have a height different from the height of the reaction force generation members for the black keys can be configured such that the body portions for the white keys have the same or roughly the same configuration as the body portions for the black keys. As a result, the keyboard apparatus can provide a player with roughly the same key touch both on the white keys and the black keys. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a keyboard apparatus according to the first embodiment of the present invention; 
         FIG. 2  is a schematic top view of the keyboard apparatus of  FIG. 1 ; 
         FIG. 3  is an enlarged cross sectional view of reaction force generation members seen along a line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a schematic side view of a keyboard apparatus according to the second embodiment of the present invention; 
         FIG. 5  is a schematic top view of the keyboard apparatus of  FIG. 4 ; 
         FIG. 6  is an enlarged cross sectional view of reaction force generation members seen along a line  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a schematic side view of a keyboard apparatus according to the third embodiment of the present invention; 
         FIG. 8  is a schematic top view of the keyboard apparatus of  FIG. 7 ; 
         FIG. 9  is an enlarged cross sectional view of reaction force generation members seen along a line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is an enlarged cross sectional view of a modification of the reaction force generation members of the third embodiment; 
         FIG. 11  is a schematic side view of a keyboard apparatus according to the fourth embodiment of the present invention; 
         FIG. 12  is a schematic top view of the keyboard apparatus of  FIG. 11 ; 
         FIG. 13  is an enlarged cross sectional view of reaction force generation members seen along a line  13 - 13  of  FIG. 12 ; 
         FIG. 14  is an enlarged cross sectional view of a modification of the reaction force generation members of the fourth embodiment; 
         FIG. 15  is a schematic side view of a keyboard apparatus according to the fifth embodiment of the present invention; and 
         FIGS. 16(A)  and (B) are illustrations for explaining respective positions of lower end surfaces of dome portions of the reaction force generation members of a white key and a black key. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following, the invention will be further explained with the description of several embodiments of the invention. It is noted that although the embodiments do show the reaction force generation members as being embodied by an elastic dome construction, the invention is not limited to this implementation. The invention can be implemented using any suitable reaction force generation element. For example the reaction force generation element can include a spring member or an elastic element that generates a resisting force when actuated; for example a metal and/or plastic spring, a rubber and/or foam element, or an elastic rubber dome, or any other suitable material and/or construction, or combinations thereof. As in several embodiments, the reaction force generation elements can be the same for each key in the keyboard, but the invention is not limited to this implementation. Different reaction force generation elements can be used for any key, for example different ones for white and black keys, or for example different ones for the left and right side of the keyboard. 
     Further, the definition of the positions of the points (Pw, Pw′, Pb, Pb′) of intersection, which is described in the summary of the invention, will be explained as follows. The definition of the positions of the points of intersection were provided in order to define a difference in the direction of axis line between the lower end surface of the dome portion of the white key and the lower end surface of the dome portion of the black key. This will be explained with reference to  FIG. 16 . As indicated  FIG. 16(A) , a case where the axis line Yw of the dome portion  21   w   1  of the reaction force generation member  21   w  of the white key  11   w  is parallel with the axis line Yb of the dome portion  21   b   1  of the reaction force generation member  21   b  of the black key  11   b  will be explained. In this case, a difference ΔL in distance in the direction of the axis lines Yw and Yb between the respective lower end surfaces of the dome portions  21   w   1  and  21   b   1  can be defined as a distance in the direction of the axis lines Yw and Yb between the intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and the intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb. The difference ΔL in distance can be also defined as a difference in distance between the intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and an intersection point Pb′ between the lower end surface of the dome portion  21   b   1  and the axis line Yw, and can be also defined as a difference in distance between an intersection point Pw′ between the lower end surface of the dome portion  21   w   1  and the axis line Yb, and the intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb. 
     As indicated in  FIG. 16(B) , however, there are cases where the reaction force generation member  21   b  for the black key is assembled such that the reaction force generation member  21   b  for the black key is inclined against the reaction force generation member  21   w  for the white key. In such cases, the axis lines Yw and Yb are not parallel with each other. In such cases, therefore, the difference between the position of the lower end surface of the dome portion  21   w   1  in the direction of the axis line Yw and the position of the lower end surface of the dome portion  21   b   1  in the direction of the axis line Yb cannot be defined by use of the axis lines Yw and Yb. Therefore, the difference in position of the respective lower end surfaces of the dome portions  21   w   1  and  21   b   1  will be defined by use of either of the axis line Yw of the dome portion  21   w   1  or the axis line Yb of the dome portion  21   b   1 , including the case where the axis lines Yw and Yb are parallel with each other. More specifically, a distance in the direction of the axis line Yw between the intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and the intersection point Pb′ between the lower end surface of the dome portion  21   b   1  and the axis line Yw will be defined. Alternatively, a distance in the direction of the axis line Yb between the intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb, and the intersection point Pw′ between the lower end surface of the dome portion  21   w   1  and the axis line Yb will be defined. In this case as well, furthermore, since the inclination of the axis line Yb against the axis line Yw is exaggerated in  FIG. 16(B) , there substantially exists a distance in the direction of the axis line Yw (or the axis line Yb) between the lower end surface of the dome portion  21   w   1  and the lower end surface of the dome portion  21   b   1  as in the case of  FIG. 16(A) . 
     a. First Embodiment 
     The first embodiment of the present invention will now be described with reference to the drawings.  FIG. 1  is a schematic side view indicative of a keyboard apparatus according to the first embodiment seen from the right.  FIG. 2  is a schematic top view of the keyboard apparatus. In schematic side views of the keyboard apparatus shown in  FIG. 1  and FIGS.  4 ,  7 ,  11  and  15  which will be described later, the front-rear direction of the keyboard apparatus is defined as the lateral direction, and the vertical direction of the keyboard apparatus is defined as the vertical direction. 
     The keyboard apparatus has a plurality of white keys  11   w  and a plurality of black keys  11   b  which are to be depressed and released by a player. The keyboard apparatus also has a plurality of reaction force generation members  21   w ,  21   b  each exerting a reaction force against a player&#39;s depression of its corresponding key. The white key  11   w  is long in the front-rear direction, has a U-shaped cross-section which is open downward, and is located on a flat upper plate portion  31   a  of a key frame  31 . The key frame  31  has flat leg portions  31   b  and  31   c  extending downward at the front end and the rear end of the upper plate portion  31   a , with respective lower end portions of the leg portions  31   b  and  31   c  being fastened to a frame FR provided within a musical instrument. To the upper surface of the rear end portion of the upper plate portion  31   a  of the key frame  31 , a pair of plate-like key supporting portions  32  erected to be opposed with each other inside the white key  11   w  is fastened. On the upper portion of each key supporting portion  32 , a projecting portion jutting outward is provided to face each other. The projecting portion of each key supporting portion  32  is inserted into a through-hole provided on the both sides of the rear end portion of the white key  11   w  from inside the white key  11   w  so that the key can rotate. By such a configuration, the white key  11   w  is supported by the pair of key supporting portions  32  so that the white key  11   w  can pivot to allow the front end of the white key  11   w  to move in the vertical direction. Hereafter, the center of the pivoting of the white key  11   w  will be referred to as a pivot axis Cw. The black keys  11   b  are configured similarly to the white keys  11   w , except that the black keys  11   b  are configured to have a raised upper face of the front portion. Each of the black keys  11   b  is also supported by the key supporting portions  32  so that the black key  11   b  can pivot about a pivot axis Cb to allow the front end of the black key  11   b  to move in the vertical direction. In this embodiment, the pivot axis Cb of the black key  11   b  is situated at the same position in the front-rear direction and in the vertical direction as the pivot axis Cw of the white key  11   w.    
     On the upper surface of the upper plate portion  31   a  of the key frame  31 , a key guide  33   w  is erected to be situated under the front end portion of the white key  11   w , while a key guide  33   b  is erected to be situated under the front end portion of the black key  11   b . The key guides  33   w  and  33   b  are inserted into the white key  11   w  and the black key  11   b , respectively, so that the key guides  33   w  and  33   b  can slide in order to prevent the white key  11   w  and the black key  11   b  from moving in the lateral direction when the keys  11   w  and  11   b  pivot in the vertical direction. 
     A reaction force generation member  21   w  is provided for each of the white keys  11   w , while a reaction force generation member  21   b  is provided for each of the black keys  11   b . The reaction force generation members  21   w  and  21   b  are fastened to the upper surface of the upper plate portion  31   a  of the key frame  31  such that the reaction force generation member  21   w  and  21   b  are situated below a central portion of the white key  11   w  and the black key  11   b , respectively, in the front-rear direction. In this case, the reaction force generation member  21   w  of the white key  11   w  is located on the same position in the front-rear direction as the reaction force generation member  21   b  of the black key  11   b , so that the reaction force generation members  21   w  and  21   b  are arranged in a row in the lateral direction of the keyboard. Furthermore, the reaction force generation members  21   w  and  21   b  are integrally formed in one piece. 
     Hereafter, the reaction force generation members  21   w  and  21   b  will be explained.  FIG. 3  is an enlarged cross-sectional view of the reaction force generation members seen along a line  3 - 3  of  FIG. 2 . The plurality of reaction force generation members  21   w  and  21   b  are integrally formed of elastic rubber. The reaction force generation members  21   w  and  21   b  have dome portions  21   w   1  and  21   b   1 , top portions  21   w   2  and  21   b   2 , and base portions  21   w   3  and  21   b   3 , respectively. The dome portions  21   w   1  and  21   b   1  are point-symmetric about axis lines Yw and Yb, respectively, to be shaped like a dome (a bowl) which is thin and deformable by depression from above. Conversely, the axis lines Yw and Yb are central axes of the dome portions  21   w   1  and  21   b   1 , and the top portions  21   w   2  and  21   b   2 , respectively. Furthermore, the axis lines Yw and Yb are lines of action of force, the lines each passing through the starting point of the reaction force vector to extend in a vector direction. More specifically, the dome portions  21   w   1  and  21   b   1  are elastically deformed by an increasing depression from above to gradually increase a reaction force. After the reaction force has reached its peak, however, the dome portions  21   w   1  and  21   b   1  buckle to sharply decrease the reaction force to gradually increase the reaction force. The dome portion  21   w   1  and the dome portion  21   b   1  have the same shape. Particularly, a distance Lw ranging from the lower end surface to the upper end surface of the dome portion  21   w   1  is equal to a distance Lb ranging from the lower end surface to the upper end surface of the dome portion  21   b   1 . The dome portions  21   w   1  and  21   b   1  are equivalent to body portions of the present invention, seen from a different viewpoint. 
     The top portions  21   w   2  and  21   b   2  are point-symmetric about the axis lines Yw and Yb, respectively, to be shaped like a cylinder. Furthermore, the top portions  21   w   2  and  21   b   2  are thick so that the top portions  21   w   2  and  21   b   2  are hardly deformed by depression from above. The top portions  21   w   2  and  21   b   2  are designed such that the undersurfaces of the top portions  21   w   2  and  21   b   2  are connected with the upper surfaces of the dome portions  21   w   1  and  21   b   1 , respectively, while the top portions  21   w   2  and  21   b   2  have a uniform height at all circumferences to have a flat upper surface. At a circumferential part of the upper portion of the top portions  21   w   2  and  21   b   2 , a notch (not shown) is provided so that air can escape between the inside and the outside of the top portions  21   w   2  and  21   b   2 . The top portions  21   w   2  and  21   b   2  have the same shape. 
     The base portions  21   w   3  and  21   b   3  extend downward seamlessly from all circumferences of the lower end of the dome portions  21   w   1  and  21   b   1 , respectively, to jut outward from the lower end surface of the dome portions  21   w   1  and  21   b   1 , respectively. The base portions  21   w   3  and  21   b   3  are also thick so that the base portions  21   w   3  and  21   b   3  are hardly deformed by depression from above. The plurality of base portions  21   w   3  and  21   b   3  are seamlessly formed integrally with the neighboring base portions  21   b   3  and  21   w   3  such that the bottom surfaces of the base portions  21   w   3  and  21   b   3  form a flat surface. Although the upper surface of each of the base portions  21   w   3  and  21   b   3  is flat, a step  21   p  is provided between the upper surfaces of the base portions  21   w   3  and  21   b   3 . Because of this step, the base portion  21   w   3  for the white key  11   w  is lower than the base portion  21   b   3  of the black key  11   b.    
     On the undersurface of the base portions  21   w   3  and  21   b   3 , a plurality of leg portions  22  jutting perpendicularly downward from the undersurface of the base portions  21   w   3  and  21   b   3  to be shaped like a cylinder are provided at proper positions. The plurality of leg portions  22  are also formed integrally with the dome portions  21   w   1  and  21   b   1 , the top portions  21   w   2  and  21   b   2 , and the base portions  21   w   3  and  21   b   3  by elastic body. The leg portions  22 , which are provided in order to fasten the reaction force generation members  21   w  and  21   b  to a supporting portion  31   d  provided on the upper plate portion  31   a  of the key frame  31 , are pressed into penetrating holes provided on the supporting portion  31   d . Without using the leg portions  22 , furthermore, the undersurface of the base portions  21   w   3  and  21   b   3  may be fastened to the upper plate portion  31   a  (the supporting portion  31   d ) of the key frame  31  with an adhesive or the like. 
     Furthermore, since the upper surface of the supporting portion  31   d  is a horizontal plane, the reaction force generation members  21   w  and  21   b  are fastened to the upper surface of the supporting portion  31   d , with the axis lines Yw and Yb being kept parallel with each other and vertical with respect to the supporting portion  31   d . As a result, by the difference in the height between the base portions  21   w   3  and  21   b   3  brought about by the step  21   p , the upper surface of the top portion  21   w   2  of the reaction force generation member  21   w  is lower than the upper surface of the top portion  21   b   2  of the reaction force generation member  21   b  in the state where the reaction force generation members  21   w  and  21   b  are fastened to the upper surface of the supporting portion  31   d . The difference in height is adjusted such that the amount of downward travel of the upper surface of the front end of the white key  11   w  by the depression of the white key  11   w  is roughly the same as the amount of downward travel of the upper surface of the front end of the black key  11   b  by the depression of the black key  11   b  at the start of deformation of the reaction force generation member  21   w  (the dome portion  21   w   1 ) and the reaction force generation member  21   b  (the dome portion  21   b   1 ), at respective peaks of the reaction forces of the reaction force generation members  21   w  and  21   b , and at the end of the deformation of the reaction force generation members  21   w  and  21   b.    
     On the undersurfaces of the white key  11   w  and the black key  11   b , depression portions  11   w   1  and  11   b   1  for depressing the reaction force generation members  21   w  and  21   b  from above are provided, respectively, such that the depression portions  11   w   1  and  11   b   1  face the upper surfaces of the top portions  21   w   2  and  21   b   2  of the reaction force generation members  21   w  and  21   b , respectively. Each of the depression portions  11   w   1  and  11   b   1  is shaped like a flat plate, and has an undersurface which is flat and is tilted such that the front side is high, and the rear side is low with respect to the undersurface of the white key  11   w  and the black key  11   b . The tilting angle of the depression portions  11   w   1  and  11   b   1  is designed such that the normal lines of the undersurfaces of the depression portions  11   w   1  and  11   b   1  (straight lines perpendicular to the undersurfaces) become parallel to the axis lines Yw and Yb of the reaction force generation members  21   w  and  21   b  when the reaction forces of the reaction force generation members  21   w  and  21   b  reach their peaks, respectively. At the points in time when the reaction forces of the reaction force generation members  21   w  are  21   b  reach their peaks, respectively, furthermore, the directions in which the reaction forces act coincide with the directions of the axis lines Yw and Yb of the reaction force generation members  21   w  and  21   b , respectively. Therefore, it can be understood that at the points in time when the reaction forces of the reaction force generation members  21   w  and  21   b  reach their peaks, respectively, the direction in which the reaction force acts is different between the white key  11   w  and the black key  11   b , while the directions in which the reaction force generation members  21   w  and  21   b  are depressed at the points in time when the reaction forces of the reaction force generation members  21   w  and  21   b  reach their peaks coincide with the directions in which the reaction force generation members  21   w  and  21   b  exert a reaction force, respectively. In this case, the inclination of the undersurface of the depression portion  11   b   1  of the black key  11   b  against the horizontal surface (the undersurface of the black key  11   b ) is slightly greater than the inclination of the undersurface of the depression portion  11   w   1  of the white key  11   w  against the horizontal surface (the undersurface of the white key  11   w ). The respective undersurfaces of the depression portions  11   w   1  and  11   b   1  may not be flat but may be spherical as long as the normal lines of the undersurfaces including respective depression points of the depression portions  11   w   1  and  11   b   1  become parallel to the axis lines Yw and Yb, respectively, at the points in time when the reaction forces reach their peaks, respectively. Furthermore, the depression portions  11   w   1  and  11   b   1  may be a rib shaped like a cross, a letter H or the like protruding downward from the inner upper surface of the white key  11   w  and the black key  11   b , respectively. 
     Furthermore, the keyboard apparatus has a spring  34   w  for the white key  11   w  and a spring  34   b  for the black key  11   b . The springs  34   w  and  34   b  are provided between the white key  11   w  and the black key  11   b , and the upper plate portion  31   a  of the key frame  31 , respectively, such that the springs  34   w  and  34   b  are situated at the midpoint between the depression portions  11   w   1  and  11   wb , and the key supporting portions  32 , respectively. The springs  34   w  and  34   b  urge the white key  11   w  and the black key  11   b  upward, respectively, with respect to the upper plate portion  31   a . The springs  34   w  and  34   b  may not be a coil, but may be a plate spring as long as the springs can urge the white key  11   w  and the black key  11   b  upward. 
     The white key  11   w  has an extending portion  11   w   2  which extends downward from the front end of the white key  11   w . At the lower end of the extending portion  11   w   2 , an engagement portion  11   w   3  jutting frontward is provided such that the engagement portion  11   w   3  is inserted below the upper plate portion  31   a  from above through a through-hole provided on the upper plate portion  31   a  of the key frame  31 . On the undersurface of a front end portion of the upper plate portion  31   a  of the key frame  31 , an upper limit stopper member  35   w  is provided. The upper limit stopper member  35   w  is a cushioning material such as felt. By coming into contact with the engagement portion  11   w   3  of the white key  11   w , the upper limit stopper member  35   w  restricts upward displacement of the front end portion of the white key  11   w . On the upper surface of the front end portion of the upper plate portion  31   a  of the key frame  31 , a lower limit stopper member  36   w  is provided. The lower limit stopper member  36   w  is also a cushioning material such as felt. By coming into contact with the undersurface of the front end portion of the white key  11   w , the lower limit stopper member  36   w  restricts downward displacement of the front end portion of the white key  11   w.    
     The black key  11   b  has an extending portion  11   b   2  which extends downward from the front end of the black key  11   b . At the lower end of the extending portion  11   b   2 , an engagement portion  11   b   3  jutting rearward is provided such that the engagement portion  11   b   3  is inserted below the upper plate portion  31   a  from above through a through-hole provided on the upper plate portion  31   a  of the key frame  31 . On the undersurface of a middle portion of the upper plate portion  31   a  of the key frame  31 , an upper limit stopper member  35   b  is provided. The upper limit stopper member  35   b  is also a cushioning material such as felt. By coming into contact with the engagement portion  11   b   3  of the black key  11   b , the upper limit stopper member  35   b  restricts upward displacement of the front end portion of the black key  11   b . On the upper surface of the middle portion of the upper plate portion  31   a  of the key frame  31 , a lower limit stopper member  36   b  is provided. The lower limit stopper member  36   b  is also a cushioning material such as felt. By coming into contact with the undersurface of the front end portion of the black key  11   b , the lower limit stopper member  36   b  restricts downward displacement of the front end portion of the black key  11   b.    
     To the undersurface of the upper plate portion  31   a  of the key frame  31 , electric circuit boards  37  are fastened such that the electric circuit boards  37  are situated slightly behind the reaction force generation members  21   w  and  21   b , respectively, to be parallel to the upper plate portion  31   a . To the upper surface of the electric circuit boards  37 , dome-shaped key switches  38   w  and  38   b  for the white key  11   w  and the black key  11   b  are fastened, respectively. The key switches  38   w  and  38   b  are changed from an off-state to an on-state by a depression of a jutting portion jutting from the undersurface of the white key  11   w  and the black key  11   b  at the time of a depression of a key to detect a user&#39;s depression/release of the white key  11   w  and the black key  11   b . The detection of the depression/release of a key by the key switch  38   w  and  38   b  is used for control of generation of a musical tone signal. 
     Next, the operation of the keyboard apparatus according to the first embodiment configured as above will be explained. When a player starts depressing the white key  11   w  or the black key  11   b , the depressed white key  11   w  or black key  11   b  starts pivoting about the pivot axis Cw or Cb, resisting a reaction force exerted by the spring  34   w  or  34   b , so that the front end portion of the white key  11   w  or the black key  11   b  moves downward to allow the engagement portion  11   w   3  or  11   b   3  to be released from the upper limit stopper member  35   w  or  35   b  to allow the depression portion  11   w   1  or  11   b   1  to come into contact with the rear end of the upper surface of the top portion  21   w   2  or  21   b   2  of the reaction force generation member  21   w  or  21   b . If the depressed white key  11   w  or black key  11   b  is depressed further, the front end portion of the white key  11   w  or the black key  11   b  moves downward, so that the dome portion  21   w   1  or  21   b   1  of the reaction force generation member  21   w  or  21   b  starts being deformed by the depression by the depression portion  11   w   1  or  11   b   1 . As a result, the player starts recognizing not only the reaction force exerted by the spring  34   w  or  34   b  but also the gradually increasing reaction force exerted by the reaction force generation member  21   w  or  21   b.    
     If the depressed white key  11   w  or black key  11   b  is depressed further, the reaction force of the reaction force generation member  21   w  or  21   b  reaches its peak, so that the dome portion  21   w   1  or  21   b   1  starts buckling and deforming. As a result, the player can recognize a clear feeling of click. Slightly later than the buckling, furthermore, the key switch  38   w  or  38   b  turns from the off-state to the on-state by a depression of the jutting portion jutting from the undersurface of the white key  11   w  or the black key  11   b . In response to the change to the on-state of the key switch  38   w  or  38   b , a musical tone signal generation circuit which is not shown starts generating a musical tone signal. 
     If the depressed white key  11   w  or black key  11   b  is depressed further, the undersurface of the front end portion of the white key  11   w  or the black key  11   b  comes into contact with the lower limit stopper member  36   w  or  36   b  to stop the pivoting of the white key  11   w  or the black key  11   b . In this state, the elastic deformation of the reaction force generation member  21   w  or  21   b  also stops. If the white key  11   w  or the black key  11   b  is released, the front end portion of the white key  11   w  or the black key  11   b  moves upward because of the reaction forces of the reaction force generation member  21   w  or  21   b  and the spring  34   w  or  34   b . In the course during which the front end portion of the white key  11   w  or the black key  11   b  moves to return upward, the key switch  38   w  or  38   b  changes from the on-state to the off-state, so that the musical tone signal generation circuit which is not shown controls the termination of the generation of the musical tone signal. If the front end portion of the white key  11   w  or the black key  11   b  moves upward, furthermore, the engagement portion  11   w   3  or  11   b   3  comes into contact with the upper limit stopper member  35   w  or  35   b  to allow the white key  11   w  or the black key  11   b  to return to the key-release state. 
     The keyboard apparatus configured to operate as above is designed such that because of the difference in thickness between the base portion  21   w   3  (the length in the direction of the axis line Yw) and the base portion  21   b   3  (the length in the direction of the axis line Yb), the amount of downward travel of the upper surface of the front end of the white key  11   w  by the depression of the white key  11   w  is roughly the same as the amount of downward travel of the upper surface of the front end of the black key  11   b  by the depression of the black key  11   b  at the start of deformation of the reaction force generation member  21   w  (the dome portion  21   w   1 ) and the reaction force generation member  21   b  (the dome portion  21   b   1 ), at respective peaks of the reaction forces of the reaction force generation members  21   w  and  21   b , and at the end of the deformation of the reaction force generation members  21   w  and  21   b . In spite of the difference in structure between the white key  11   w  and the black key  11   b , as a result, a player of the keyboard apparatus can operate both the white key  11   w  and the black key  11   b  without any feeling of strangeness. 
     The keyboard apparatus is also designed such that the dome portion  21   w   1  and the top portion  21   w   2  have the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2 , respectively, although the height of the lower end surface of the dome portion is different between the dome portion  21   w   1  and the dome portion  21   b   1  because of the difference in height between the base portion  21   w   3  and the base portion  21   b   3 . As a result, the keyboard apparatus can provide the player with almost the same key touch on both the white key  11   w  and the black key  11   b . In the first embodiment, furthermore, the plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  are formed integrally in one piece so that the integrally formed reaction force generation members  21   w  and  21   b  can be assembled easily. 
     In the above explanation, the difference in height of the lower end surface of the dome portion between the dome portion  21   w   1  of the white key  11   w  and the dome portion  21   b   1  of the black key  11   b  was explained with reference to the upper surface of the supporting portion  31   d . Instead of the above explanation, however, the difference will now be explained, using the points of intersection between the respective lower end surfaces of the dome portions  21   w   1  and  21   b   1 , and the axis lines Yw and Yb. In the above case, the axis line Yw of the dome portion  21   w   1  of the reaction force generation member  21   w  of the white key  11   w  is parallel with the axis line Yb of the dome portion  21   b   1  of the reaction force generation member  21   b  of the black key  11   b  as indicated in  FIG. 3  and  FIG. 16(A) . In this case, therefore, a difference ΔL in distance in the direction of the axis lines Yw and Yb between the respective lower end surfaces of the dome portions  21   w   1  and  21   b   1  can be defined as a distance in the direction of the axis lines Yw and Yb between an intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and an intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb. The difference ΔL in distance can be also defined as a difference in distance between the intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and an intersection point Pb′ between the lower end surface of the dome portion  21   b   1  and the axis line Yw, and can be also defined as a difference in distance between an intersection point Pw′ between the lower end surface of the dome portion  21   w   1  and the axis line Yb, and the intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb. 
     As indicated in  FIG. 16(B) , however, there are cases where the reaction force generation member  21   b  for the black key is assembled such that the reaction force generation member  21   b  for the black key is inclined against the reaction force generation member  21   w  for the white key. In such cases, since the axis lines Yw and Yb are not parallel with each other, it is difficult to define the difference in height of the lower end surface between the dome portions  21   w   1  and  21   b   1  by the above-described scheme. In this specification, therefore, the difference in position of the respective lower end surfaces of the dome portions  21   w   1  and  21   b   1  will be defined by use of either of the axis line Yw of the dome portion  21   w   1  or the axis line Yb of the dome portion  21   b   1 , including the case where the axis lines Yw and Yb are parallel with each other. More specifically, a distance in the direction of the axis line Yw between the intersection point Pw between the lower end surface of the dome portion  21   w   1  and the axis line Yw, and the intersection point Pb′ between the lower end surface of the dome portion  21   b   1  and the axis line Yw will be defined. Alternatively, a distance in the direction of the axis line Yb between the intersection point Pb between the lower end surface of the dome portion  21   b   1  and the axis line Yb, and the intersection point Pw′ between the lower end surface of the dome portion  21   w   1  and the axis line Yb will be defined. In this case as well, furthermore, since the inclination of the axis line Yb against the axis line Yw is exaggerated in  FIG. 16(B) , there substantially exists a distance in the direction of the axis line Yw (or the axis line Yb) between the lower end surface of the dome portion  21   w   1  and the lower end surface of the dome portion  21   b   1  as in the case of  FIG. 16(A) . The respective lower end surfaces of the dome portions  21   w   1  and  21   b   1  are positioned similarly in embodiments which will be described later. 
     The above-described first embodiment is designed such that the dome portion  21   w   1  and the top portion  21   w   2  have exactly the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2 , respectively, but may have a slightly different shape, as in the case of the above-described inclination. 
     Furthermore, the first embodiment is configured such that the reaction force generation members  21   w  and  21   b  are fastened to the supporting portion  31   d  so that the reaction force generation members  21   w  and  21   b  can be depressed by the depression portions  11   w   1  and  11   b   1  of the white key  11   w  and the black key  11   b , respectively. Instead of this configuration, however, the reaction force generation members  21   w  and  21   b  may be fastened to the white key  11   w  and the black key  11   b , respectively, with depression portions being provided on the upper plate portion  31   a  of the key frame  31  to be opposed to the reaction force generation members  21   w  and  21   b , respectively, so that the reaction force generation members  21   w  and  21   b  can be depressed by the depression portions by the pivoting white key  11   w  and the pivoting black key  11   b , respectively. In this modification, it is necessary to form each of the reaction force generation members  21   w  and  21   b  separately to be individually fastened to the white key  11   w  and the black key  11   b.    
     b. Second Embodiment 
     Next, a keyboard apparatus according to the second embodiment in which the plurality of reaction force generation members  21   w  of the white keys  11   w  and the plurality of reaction force generation members  21   b  of the black keys  11   b  are arranged in two rows such that the reaction force generation members  21   w  are displaced in the front-rear direction from the reaction force generation members  21   b  will be explained.  FIG. 4  is a schematic side view of the keyboard apparatus according to the second embodiment seen from the right.  FIG. 5  is a schematic top view of the keyboard apparatus.  FIG. 6  is an enlarged cross-sectional view indicating the reaction force generation member  21   w  of the white key  11   w  and the reaction force generation member  21   b  of the black key  11   b  seen along lines  6 - 6  shown in  FIG. 5 . 
     The plurality of reaction force generation members  21   w  are arranged in the lateral direction on a supporting portion  31   d   1  provided on the upper plate portion  31   a  of the key frame  31 . The supporting portion  31   d   1  extends in the lateral direction such that the supporting portion  31   d   1  is slightly lower than the upper plate portion  31   a . The plurality of reaction force generation members  21   w  are formed integrally by elastic body in one piece, with each of the reaction force generation members  21   w  having the dome portion  21   w   1 , the top portion  21   w   2  and the base portion  21   w   3  which are similar to those of the first embodiment. The plurality of dome portions  21   w   1  and top portions  21   w   2  are situated below the depression portions  11   w   1  of the white keys  11   w . The base portions  21   w   3  are configured to have the same thickness to be shaped like a flat plate to be connected with the dome portions  21   w   1 . 
     The plurality of reaction force generation members  21   b  are arranged in the lateral direction on a supporting portion  31   d   2  provided on the upper plate portion  31   a  of the key frame  31 . The supporting portion  31   d   2  extends in the lateral direction such that the supporting portion  31   d   2  is situated behind the supporting portion  31   d   1 , and is as high as the upper plate portion  31   a . The plurality of reaction force generation members  21   b  are also formed integrally by elastic body in one piece, with each of the reaction force generation members  21   b  having the dome portion  21   b   1 , the top portion  21   b   2  and the base portion  21   b   3  which are similar to those of the first embodiment. The plurality of dome portions  21   b   1  and top portions  21   b   2  are situated below the depression portions  11   b   1  of the black keys  11   b . The depression portions  11   b   1  of the black keys  11   b  are situated behind the depression portions  11   w   1  of the white keys  11   w . The base portions  21   b   3  are configured to have the same thickness to be shaped like a flat plate to be connected with the dome portions  21   b   1 . In this case, the reaction force generation members  21   w  of the white keys  11   w  are provided separately from the reaction force generation members  21   b  of the black keys  11   b , but have the same shape as the reaction force generation members  21   b  of the black keys  11   b . Particularly, the base portions  21   w   3  and  21   b   3  have the same thickness, and the dome portion  21   w   1  and the top portion  21   w   2  have the same shapes as the dome portion  21   b   1  and the top portion  21   b   2 , respectively. 
     In the second embodiment, furthermore, because of the difference in vertical position between the supporting portions  31   d   1  and  31   d   2 , the upper surface of the top portion  21   w   2  of the reaction force generation member  21   w  is lower than the upper surface of the top portion  21   b   2  of the reaction force generation member  21   b . The difference in vertical position is adjusted, similarly to the first embodiment, such that the amount of downward travel of the upper surface of the front end of the white key  11   w  by the depression of the white key  11   w  is roughly the same as the amount of downward travel of the upper surface of the front end of the black key  11   b  by the depression of the black key  11   b  at the start of deformation of the reaction force generation member  21   w  (the dome portion  21   w   1 ) and the reaction force generation member  21   b  (the dome portion  21   b   1 ), at respective peaks of the reaction forces of the reaction forces of the reaction force generation members  21   w  and  21   b , and at the end of the deformation of the reaction force generation members  21   w  and  21   b . Since the other configuration of the second embodiment is similar to the first embodiment, components of the second embodiment are given the same numerals as those of the first embodiment to omit their explanations. 
     In response to the player&#39;s depression and release of the white key  11   w  and the black key  11   b , the keyboard apparatus according to the second embodiment configured as above also operates similarly to the first embodiment. Furthermore, the second embodiment is configured such that because of the difference in vertical position between the supporting portion  31   d   1  and the supporting portion  31   d   2 , the player of the keyboard apparatus of the second embodiment can depress and release both the white key  11   w  and the black key  11   b  without any feeling of strangeness, and can perceive roughly the same key touch on the white keys  11   w  and the black keys  11   b  in spite of the difference in structure between the white key  11   w  and the black key  11   b , because of the reason similar to that of the first embodiment. In the second embodiment, furthermore, the plurality of reaction force generation members  21   w  are formed integrally in one piece, while the plurality of reaction force generation members  21   b  are also formed integrally in one piece. Therefore, the integrally formed reaction force generation members  21   w  and  21   b  can be assembled easily. 
     The above-described second embodiment is also designed such that the dome portion  21   w   1  and the top portion  21   w   2  have exactly the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2 , respectively, but may have a slightly different shape, as in the case of the first embodiment. 
     Furthermore, the second embodiment is also configured such that the reaction force generation members  21   w  and  21   b  are fastened to the supporting portions  31   d   1  and  31   d   2 , respectively, so that the reaction force generation members  21   w  and  21   b  can be depressed by the depression portions  11   w   1  and  11   b   1  of the white key  11   w  and the black key  11   b , respectively. Instead of this configuration, however, the reaction force generation members  21   w  and  21   b  may be fastened to the white key  11   w  and the black key  11   b , respectively, with depression portions being provided on the upper plate portion  31   a  of the key frame  31  to be opposed to the reaction force generation members  21   w  and  21   b , respectively, so that the reaction force generation members  21   w  and  21   b  can be depressed by the depression portions by the pivoting white key  11   w  and the pivoting black key  11   b , respectively. In this modification as well, it is necessary to form each of the reaction force generation members  21   w  and  21   b  separately to be individually fastened to the white key  11   w  and the black key  11   b.    
     c. Third Embodiment 
     Next, a keyboard apparatus according to the third embodiment in which the plurality of reaction force generation members  21   w  of the white keys  11   w  and the plurality of reaction force generation members  21   b  of the black keys  11   b  of the above second embodiment are integrally formed in one piece will be explained.  FIG. 7  is a schematic side view of the keyboard apparatus according to the third embodiment seen from the right.  FIG. 8  is a schematic top view of the keyboard apparatus.  FIG. 9  is an enlarged cross-sectional view indicating the reaction force generation members  21   w  and  21   b  of the white key  11   w  and the black key  11   b  seen along a line  9 - 9  shown in  FIG. 8 . 
     The third embodiment is configured such that the plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  of the above second embodiment are formed integrally in one piece, while the reaction force generation members  21   w  and  21   b  have the dome portions  21   w   1  and  21   b   1 , the top portions  21   w   2  and  21   b   2 , and the base portions  21   w   3  and  21   b   3  which are similar to those of the first and second embodiments, respectively. In this embodiment, respective undersurfaces of the plurality of base portions  21   w   3  and  21   b   3  form a seamless horizontal plane to have a step  21   q  between an upper surface of the seamless base portions  21   w   3  and an upper surface of the seamless base portions  21   b   3 . The integrally formed reaction force generation members  21   w  and  21   b  are provided on the supporting portion  31   d  provided on the upper plate portion  31   a . Because of such a configuration, the upper surface of the top portion  21   w   2  of the reaction force generation member  21   w  is lower than the upper surface of the top portion  21   b   2  of the reaction force generation member  21   b . The difference in vertical position is adjusted, similarly to the first and second embodiments, such that the amount of downward travel of the upper surface of the front end of the white key  11   w  by the depression of the white key  11   w  is roughly the same as the amount of downward travel of the upper surface of the front end of the black key  11   b  by the depression of the black key  11   b  at the start of deformation of the reaction force generation member  21   w  (the dome portion  21   w   1 ) and the reaction force generation member  21   b  (the dome portion  21   b   1 ), at respective peaks of the reaction forces of the reaction force generation members  21   w  and  21   b , and at the end of the deformation of the reaction force generation members  21   w  and  21   b . Since the other configuration of the third embodiment is similar to the first embodiment, components of the third embodiment are given the same numerals as those of the first embodiment to omit their explanations. 
     In response to the player&#39;s depression and release of the white key  11   w  and the black key  11   b , the keyboard apparatus according to the third embodiment configured as above also operates similarly to the first and second embodiments. Furthermore, the third embodiment is configured such that because of the difference in thickness of the base portion, that is, in length of the base portion in the direction of the axis lines Yw and Yb between the base portion  21   w   3  of the white key  11   w  and the base portion  21   b   3  of the black key  11   b , the player of the keyboard apparatus of the third embodiment can depress and release both the white key  11   w  and the black key  11   b  without any feeling of strangeness, and can perceive roughly the same key touch on the white keys  11   w  and the black keys  11   b  in spite of the difference in structure between the white key  11   w  and the black key  11   b  because of the reason similar to that of the first and second embodiments. In the third embodiment, furthermore, the plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  are formed integrally in one piece, so that the integrally formed reaction force generation members  21   w  and  21   b  can be assembled easily. 
     The above-described third embodiment is also designed such that the dome portion  21   w   1  and the top portion  21   w   2  have exactly the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2 , respectively, but may have a slightly different shape, as in the case of the first and second embodiments. 
     The third embodiment is designed such that the step  21   q  is provided between the base portions  21   w   3  and the base portions  21   b   3 . Instead of the step  21   q , however, a slanting surface  21   r  may be provided to connect the base portions  21   w   3  with the base portions  21   b   3  to make a difference in vertical position of the lower end surface between the dome portions  21   w   1  and the dome portions  21   b   1  as indicated in  FIG. 10 . Further, this modification can be applied to the above first embodiment in which the reaction force generation members  21   w  and  21   b  are arranged in a row in the lateral direction of the keyboard. In other words, regarding the reaction force generation members  21   w  and  21   b  shown in  FIG. 3 , instead of the step  21   p , a slanting surface may be provided to connect the base portions  21   w   3  with the base portions  21   b   3  to make a difference in vertical position of the lower end surface between the dome portions  21   w   1  and the dome portions  21   b   1 . 
     Furthermore, the third embodiment and its modification are designed such that the rear end of the dome portion  21   w   1  of the white key  11   w  (the right end of the dome portion  21   w   1  in  FIG. 8 ) is situated in front of (on the left side in  FIG. 8 ) the front end of the dome portion  21   b   1  of the black key  11   b  (the left end of the dome portion  21   b   1  in  FIG. 8 ). However, the third embodiment and its modification may be modified such that the rear end of the dome portion  21   w   1  of the white key  11   w  is situated in between the front end and the rear end of the dome portion  21   b   1  of the black key  11   b . In other words, the dome portion  21   w   1  may be situated in front of the dome portion  21   b   1 , with a part of the dome portion  21   w   1  overlapping with the dome portion  21   b   1  in the front-rear direction. 
     d. Fourth Embodiment 
     Next, a keyboard apparatus according to the fourth embodiment in which respective bottom surfaces of the base portions  21   w   3  and  21   b   3  of the reaction force generation members  21   w  and  21   b  are inclined, with the supporting portion  31   d  provided on the upper plate portion  31   a  of the key frame  31  being also inclined will be explained.  FIG. 11  is a schematic side view of the keyboard apparatus according to the fourth embodiment seen from the right.  FIG. 12  is a schematic top view of the keyboard apparatus.  FIG. 13  is an enlarged cross-sectional view indicating the reaction force generation members  21   w  and  21   b  of the white key  11   w  and the black key  11   b  seen along a line  13 - 13  shown in  FIG. 12 . 
     The fourth embodiment is configured such that the supporting portion  31   d  is inclined such that the front side of the supporting portion  31   d  is lower than the rear side, while the supporting portion  31   d  is formed integrally with the upper plate portion  31   a . In the fourth embodiment, similarly to the second and third embodiments, the depression portions  11   w   1  of the white key  11   w  are located on the front side, with the depression portions  11   b   1  of the black key  11   b  being located on the rear side, so that the depression portions  11   w   1  and the depression portions  11   b   1  form two rows. More specifically, each of the depression portions  11   w  and  11   b   1  is configured such that the front side of the depression portion is higher than the rear side to be a flat surface. 
     The plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  are formed integrally in one piece, while the reaction force generation members  21   w  and  21   b  have the dome portions  21   w   1  and  21   b   1 , the top portions  21   w   2  and  21   b   2 , and the base portions  21   w   3  and  21   b   3  which are similar to those of the first to third embodiments, respectively. In this embodiment, respective undersurfaces of the plurality of base portions  21   w   3  and  21   b   3  form a seamless slanting plane, while respective upper surfaces of the base portions  21   w   3  and  21   b   3  are horizontal and flat. At the outside of the outer periphery of the dome portion  21   w   1 , a cylindrical gap  21   w   4  provided by notching the base portion  21   w   3  is provided, while a cylindrical gap  21   b   4  provided by notching the base portion  21   b   3  is provided at the outside of the outer periphery of the dome portion  21   b   1 . The width in a radial direction of the gaps  21   w   4  and  21   b   4  is set to be within an extent which prevents the outer periphery of the dome portions  21   w   1  and  21   b   1  from coming into contact with the inner surface of the gaps  21   w   4  and  21   b   4  when the dome portions  21   w   1  and  21   b   1  are deformed by the top portions  21   w   2  and  21   b   2  depressed from above, respectively. 
     In this embodiment, the height of the dome portions  21   w   1  and  21   b   1  indicates the height measured from the bottom surface of the gaps  21   w   4  and  21   b   4  to the upper surface of the dome portions  21   w   1  and  21   b   1 , respectively. Furthermore, the fourth embodiment is designed such that by making the depth of the gap  21   w   4  deeper than the gap  21   b   4 , the height of the dome portion  21   w   1  and the top portion  21   w   2  is lower than the height of the dome portion  21   b   1  and the top portion  21   b   2 . The dome portion  21   w   1  and the top portion  21   w   2  have the same shape as the dome portion  21   b   1  and the top portion  21   b   2 , so that a distance Lw between the lower end surface to the upper end surface of the dome portion  21   w   1  is equal with a distance Lb between the lower end surface to the upper end surface of the dome portion  21   b   1 . The difference in height between the dome portions  21   w   1  and  21   b   1  is adjusted, similarly to the first to third embodiments, such that the amount of downward travel of the upper surface of the front end of the white key  11   w  by the depression of the white key  11   w  is roughly the same as the amount of downward travel of the upper surface of the front end of the black key  11   b  by the depression of the black key  11   b  at the start of deformation of the reaction force generation member  21   w  (the dome portion  21   w   1 ) and the reaction force generation member  21   b  (the dome portion  21   b   1 ), at respective peaks of the reaction forces of the reaction force generation members  21   w  and  21   b , and at the end of the deformation of the reaction force generation members  21   w  and  21   b . Since the other configuration of the fourth embodiment is similar to the first to third embodiments, components of the fourth embodiment are given the same numerals as those of the first to third embodiments to omit their explanations. 
     In response to the player&#39;s depression and release of the white key  11   w  and the black key  11   b , the keyboard apparatus according to the fourth embodiment configured as above also operates similarly to the first to third embodiments. Furthermore, the fourth embodiment is configured such that because of the difference in depth of the gap between the gap  21   w   4  and the gap  21   b   4 , the player of the keyboard apparatus of the fourth embodiment can depress and release both the white key  11   w  and the black key  11   b  without any feeling of strangeness, and can perceive roughly the same key touch on the white keys  11   w  and the black keys  11   b  in spite of the difference in structure between the white key  11   w  and the black key  11   b  because of the reason similar to that of the first to third embodiments. In the fourth embodiment, furthermore, the plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  are formed integrally in one piece, with respective bottom surfaces of the base portions  21   w   3  and  21   b   3  being seamlessly inclined, so that the integrally formed reaction force generation members  21   w  and  21   b  can be easily provided on the inclined supporting portion  31   d.    
     The above-described fourth embodiment is also designed such that the dome portion  21   w   1  and the top portion  21   w   2  have exactly the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2 , respectively, but may have a slightly different shape, as in the cases of the first to third embodiments. 
     In the fourth embodiment, furthermore, the difference in depth between the gaps  21   w   4  and  21   b   4  makes a difference in height between the dome portion  21   w   1  and the top portion  21   w   2 , and the dome portion  21   b   1  and the top portion  21   b   2 . However, the fourth embodiment may be modified as indicated in  FIG. 14  such that without the gaps  21   w   4  and  21   b   4 , the step  21   q  is provided between the upper surface of the base portions  21   w   3  and the upper surface of the base portions  21   b   3 , with the undersurface of the base portions  21   w   3  and  21   b   3  being inclined. By this modification as well, the dome portion  21   w   1  and the top portion  21   w   2  can have the same shape as the dome portion  21   b   1  and the top portion  21   b   2 , with different height between the dome portion  21   w   1  and the top portion  21   w   2 , and the dome portion  21   b   1  and the top portion  21   b   2 . Instead of the step  21   q , similarly to the modification of the third embodiment, the slanting surface  21   r  may be provided to connect the base portions  21   w   3  with the base portions  21   b   3  to make a difference in the vertical position of the lower end surface between the dome portion  21   w   1  and the dome portion  21   b   1  (see  FIG. 10 ). 
     Furthermore, the fourth embodiment and its modifications are designed such that the rear end of the dome portion  21   w   1  of the white key  11   w  (the right end of the dome portion  21   w   1  in  FIG. 12 ) is situated in front of (on the left side in  FIG. 12 ) the front end of the dome portion  21   b   1  of the black key  11   b  (the left end of the dome portion  21   b   1  in  FIG. 12 ). However, the fourth embodiment and its modifications may also be modified such that the rear end of the dome portion  21   w   1  of the white key  11   w  is situated in between the front end and the rear end of the dome portion  21   b   1  of the black key  11   b . In other words, the dome portion  21   w   1  may be situated in front of the dome portion  21   b   1 , with a part of the dome portion  21   w   1  overlapping with the dome portion  21   b   1  in the front-rear direction. 
     e. Fifth Embodiment 
     Next, the fifth embodiment in which pivoting bodies which pivot in conjunction with pivoting of the white key  11   w  and the black key  11   b  depress the reaction force generation members  21   w  and  21   b  will be explained.  FIG. 15  indicates a keyboard apparatus according to the fifth embodiment. The keyboard apparatus has hammers  41   w  and  41   b  which are the above-described pivoting bodies such that the hammers  41   w  and  41   b  correspond to the white key  11   w  and the black key  11   b , respectively. 
     The hammers  41   w  and  41   b  are supported by hammer supporting members  42  provided for the respective white key  11   w  and black key  11   b  so that the hammers  41   w  and  41   b  can pivot. Each of the hammer supporting members  42  extends downward from the undersurface of the upper plate portion  31   a  such that the hammer supporting member  42  is situated at the middle of the white key  11   w  and the black key  11   b  in the front-rear direction. The hammers  41   w  and  41   b  are formed of base portions  41   w   1  and  41   b   1 , connecting rods  41   w   2  and  41   b   2 , and mass bodies  41   w   3  and  41   b   3 , respectively. The base portions  41   w   1  and  41   b   1  are supported at the middle portion thereof by the hammer supporting members  42  so that the hammers  41   w  and  41   b  can pivot about pivot axes Cw 1  and Cb 1 , respectively. More specifically, the mass bodies  41   w   3  and  41   b   3  pivot up and down. Each of the base portions  41   w   1  and  41   b   1  has bifurcated legs at the front portion. Between the legs, drive shafts  43   w   1  and  43   b   1  provided on extending portions  43   w  and  43   b  extending vertically from the undersurface of the white key  11   w  and the black key  11   b  penetrate so that the drive shafts  43   w   1  and  43   b   1  can slide, respectively. The extending portions  43   w  and  43   b  penetrate through a through-hole provided on the upper plate portion  31   a  so that the extending portions  43   w  and  43   b  can be displaced up and down. As a result, the respective front ends of the base portions  41   w   1  and  41   b   1  are to be displaced downward when the white key  11   w  and the black key  11   b  are depressed. The connecting rods  41   w   2  and  41   b   2  extend in the front-rear direction to connect the base portions  41   w   1  and  41   b   1  with the mass bodies  41   w   3  and  41   b   3 , respectively. The mass bodies  41   w   3  and  41   b   3  urge the respective front ends of the hammers  41   w  and  41   b  upward, using the mass of the mass bodies  41   w   3  and  41   b   3 , respectively. 
     Below each of the mass bodies  41   w   3  and  41   b   3 , an upper limit stopper member  44  for preventing the mass bodies  41   w   3  and  41   b   3  from moving downward is fastened to the frame FR. The upper limit stopper member  44  is also made of a cushioning material such as felt. In the key-release state, therefore, the mass bodies  41   w   3  and  41   b   3  are situated on the upper limit stopper member  44  in order to restrict upward move of the front end of the white key  11   w  and the black key  11   b . Therefore, the keyboard apparatus of the fifth embodiment does not have the upper limit stopper members  35   w  and  35   b , and the extending portions  11   w   2  and  11   b   2  provided for the first embodiment. 
     The reaction force generation members  21   w  and  21   b  are fastened to the respective undersurfaces of supporting portions  31   fw  and  31   fb  provided on the upper plate portion  31   a  such that the reaction force generation members  21   w  and  21   b  are opposed to the mass bodies  41   w   3  and  41   b   3 , respectively. The respective upper surfaces of the mass bodies  41   w   3  and  41   b   3  serve as flat depression portion  41   w   4  and  41   b   4 , respectively, to face the undersurfaces (equivalent to the upper surfaces of the first to fourth embodiments) of the top portions  21   w   2  and  21   b   2  of the reaction force generation members  21   w  and  21   b  in the key-release state. When the keys are depressed, the depression portions  41   w   4  and  41   b   4  move upward to come into contact with the undersurface of the top portions  21   w   2  and  21   b   2  to depress the reaction force generation members  21   w  and  21   b , respectively. In this case as well, the reaction force generation members  21   w  and  21   b  are elastically deformed by the depression to buckle after the reaction forces reach their peaks, respectively. Furthermore, since the hammers  41   w  and  41   b  exert a reaction force against the depression of the white key  11   w  and the black key  11   b , respectively, the keyboard apparatus of the fifth embodiment may have the springs  34   w  and  34   b  provided for the first embodiment, but does not have the springs  34   w  and  34   b  in the fifth embodiment. 
     In the fifth embodiment as well, the reaction force generation members  21   w  and  21   b  are configured such that because of the difference in the amount of vertical travel of the mass bodies  41   w   3  and  41   b   3  between the white key  11   w  and the black key  11   b , the respective vertical positions of the dome portion  21   w   1  and the top portion  21   w   2  are different from the respective vertical positions of the dome portion  21   b   1  and the top portion  21   b   2 , similarly to the first embodiment. The reaction force generation members  21   w  and  21   b  are configured and shaped similarly to those of the first embodiment. Since the other configuration of the fifth embodiment is similar to the first embodiment, components of the fifth embodiment are given the same numerals as those of the first embodiment to omit their explanations. 
     According to the fifth embodiment configured as above, when the white key  11   w  and the black key  11   b  are depressed, the drive shafts  43   w   1  and  43   b   1  of the extending portions  43   w  and  43   b  move downward, so that the hammers  41   w  and  41   b  pivot about the pivot axes Cw 1  and Cb 1  in the counterclockwise direction, respectively. Then, the depression portions  41   w   4  and  41   b   4  of the mass bodies  41   w   3  and  41   b   3  of the hammers  41   w  and  41   b  depress the reaction force generation members  21   w  and  21   b , respectively, so that the reaction force generation members  21   w  and  21   b  elastically deform to buckle. If the white key  11   w  and the black key  11   b  are depressed further, the reaction force generation members  21   w  and  21   b  elastically deform further, so that the depressions of the white key  11   w  and the black key  11   b  are finished by the contact between the undersurface of the front end of the white key  11   w  and the black key  11   b  and the lower limit stopper members  36   w  and  36   b . When the white key  11   w  and the black key  11   b  are depressed, the hammers  41   w  and  41   b , and the reaction force generation members  21   w  and  21   b  give reaction forces to the player against the depressions. 
     When the white key  11   w  and the black key  11   b  are released, the hammers  41   w  and  41   b  pivot in the clockwise direction because of the mass of the mass bodies  41   w   3  and  41   b   3 , respectively, so that the front end of the white key  11   w  and the black key  11   b  moves upward. If the undersurface of the mass bodies  41   w   3  and  41   b   3  comes into contact with the upper limit stopper member  44 , the white key  11   w  and the black key  11   b  stop pivoting, so that the white key  11   w  and the black key  11   b  return to the original key-release state. 
     According to the keyboard apparatus according to the fifth embodiment configured to operate as above, in spite of the difference in structure between the white key  11   w  and the black key  11   b , the player of the keyboard apparatus can depress and release both the white key  11   w  and the black key  11   b  without any feeling of strangeness, and can perceive roughly the same key touch on the white keys  11   w  and the black keys  11   b  because of the reason similar to that of the first embodiment. In the fifth embodiment, furthermore, the plurality of reaction force generation members  21   w  and the plurality of reaction force generation members  21   b  are formed integrally in one piece, so that the reaction force generation members  21   w  and  21   b  can be assembled easily. 
     The fifth embodiment may be also modified, similarly to the second to fourth embodiments and their modifications, such that the plurality of reaction force generation members  21   w  of the white keys  11   w  and the plurality of reaction force generation members  21   b  of the black keys  11   b  are laterally arranged in two rows in the front-rear direction. In this modification as well, furthermore, the plurality of reaction force generation members  21   w  may be integrally formed in one piece, with the plurality of reaction force generation members  21   b  being also integrally formed in one piece. Alternatively, the plurality of reaction force generation members  21   w  may be formed integrally with the plurality of reaction force generation members  21   b.    
     Similarly to the modifications of the first and second embodiments, furthermore, the keyboard apparatus having the hammers  41   w  and  41   b  may be modified such that the reaction force generation members  21   w  and  21   b  are fastened to the respective upper surfaces of the mass bodies  41   w   3  and  41   b   3  of the hammers  41   w  and  41   b , with depression portions for depressing the respective upper surfaces of the top portions  21   w   2  and  21   b   2  of the reaction force generation members  21   w  and  21   b  being provided on the undersurface of the upper plate portion  31   a  of the key frame  31  which faces the hammers  41   w  and  41   b , respectively. 
     f. Other Modifications 
     The first to fifth embodiments and their modifications were explained as examples in which the lower end of the dome portion  21   w   1  of the reaction force generation member  21   w  of the white key  11   w  is lower than the lower end of the dome portion  21   b   1  of the reaction force generation member  21   b  of the black key  11   b . Depending on the structure of the white keys  11   w  and the black keys  11   b , however, there can be cases where the lower end of the dome portion  21   w   1  of the reaction force generation member  21   w  of the white key  11   w  is higher than the lower end of the dome portion  21   b   1  of the reaction force generation member  21   b  of the black key  11   b.    
     The first to fifth embodiments and their modifications are configured such that the dome portion  21   w  and the top portion  21   w   2  of the reaction force generation member  21   w  of the white key  11   w  have the same shape and size as the dome portion  21   b   1  and the top portion  21   b   2  of the reaction force generation member  21   b  of the black key  11   b . However, since the top portions  21   w   2  and  21   b   2  are hardly deformed by depression, the shape and the size of the top portions  21   w   2  and  21   b   2 , particularly, the length from the upper surface to the undersurface in the direction of the axis lines Yw and Yb may be different between the top portion  21   w   2  and the top portion  21   b   2 . 
     The first to fifth embodiments and their modifications are configured such that the reaction force generation members  21   w  and  21   b  are provided separately from the key switches  38   w  and  38   b , respectively. Instead of such a configuration, however, the key switches  38   w  and  38   b  may be configured similarly to the reaction force generation members  21   w  and  21   b  so that the key switches  38   w  and  38   b  can be used as a reaction force generation member. In this modification, each of the dome portions  21   w   1  and  21   b   1  is to have a two-tier configuration having an inner portion and an outer portion, with a tubular less-deformable switch portion being provided between the inner portion and outer portion. In this modification, more specifically, by deformation of the outer portion, an increasing reaction force is generated against a depression of the key, while a contact provided on a board is opened or closed by the switch portion, with a reaction force against the key-depression being generated by deformation and buckling of the inner portion. 
     Furthermore, the first to fifth embodiments and their modifications were explained as examples in which the white keys  11   w  and the black keys  11   b  pivot about a rotational axis. However, the axis may be a hinge-type pivot axis. More specifically, the hinge-type pivot axis is configured such that a plate-like thin portion is provided on the rear end of the white key  11   w  and the black key  11   b  so that the rear end of the thin portion can be supported by a supporting member to allow the white key  11   w  and the black key  11   b  to pivot by elastic deformation of the thin portion. In this modification, however, the pivot axes Cw and Cb slightly vary with the pivoting of the white key  11   w  and the black key  11   b , respectively. That is, the respective positions of the pivot axes Cw and Cb vary with the passage of time. 
     In  FIGS. 16  A and B, the reaction force generating members are embodied as spring members  21   w  and  21   b . The spring members  21   w  and  21   b  are mounted at a mounting height with respect to the frame (for example frame  31 ) of the musical instrument that is different for the spring members  21   w  and  21   b . The difference in mounting height is denoted by delta L in  FIG. 16  A. In this embodiment the spring members are the same, and therefore the difference in mounting height is easily discernible. Also in the case of the construction of  FIG. 16  B, a difference in mounting height due to the difference in rotation can be discerned. In case that the spring members are of different type for white and black keys, the difference in mounting height can be determined by the difference in height for similar parts; if for instance the flanges  21   w   3  and  21   b   3  are shaped different (like for instance in  FIG. 9 ), but the upper sections  21   w   1  and  21   w   2 , and  21   b   1  and  21   b   2  respectively similar, then the mounting height difference can be determined by the position of the respective parts  21   w   1  and  21   w   2 , and  21   b   1  and  21   b   2 . The difference in mounting height can also be seen in the part of the spring members that elastically deforms (in this embodiment the dome shaped portion): for identical spring members the lower and upper sections are mounted at a different height. This can be determined for example by the difference in mounting height for the lower non-moving section of the spring members. For non-identical spring members the lower sections can be mounted at the same height, provided that the upper sections are of different mounting heights. Conversely, for non-identical spring members the upper sections can be mounted at the same height, provided that the lower sections are of different mounting heights.