Patent Publication Number: US-7217877-B2

Title: Keyboard apparatus

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a keyboard apparatus in which an arm is driven by a key to move to thereby apply an inertial force to the key when the key is depressed. 
   2. Description of the Related Art 
   Conventionally, a keyboard apparatus is known in which arms having mass are provided such that each of the arms moves e.g. pivotally in accordance with depression of the associated key so as to improve key touch feeling. 
   For example, a keyboard apparatus disclosed in Japanese Laid-Open Utility Model Publication (Kokai) No. H02-64992 is configured such that an arm provided with a weight is pivotally disposed on a slide member which slides in accordance with key depression, so as to transmit displacement of the associated key which is depressed to the slide member. When the key is depressed, in the first half of the key depression stroke, the associated arm is driven by the key, for pivotal motion, but halfway in the key depression stroke, the key is disengaged from the arm by a sliding motion of the slide member, and the pivotal motion of the arm is stopped. Consequently, from then on, the load of the arm is not applied to the key. 
   Further, a keyboard apparatus disclosed in Japanese Patent No. 3221283 is configured such that a driving part of a key and a driven part of the associated pivotally movable arm (mass body) are constantly held in engagement with each other, and in a key depression stroke, an inertial force of the arm is imparted to the key via the driving part and the driven part. 
   Furthermore, conventionally, keyboard apparatuses have been proposed in which touch feeling (hereinafter referred to as “key touch feeling”) can be changed. For example, in a keyboard apparatus proposed in Japanese Patent Publication (Kokoku) No. H01-47798, an arm having one end thereof engaged with a key and the other end thereof provided with a weight is configured such that the arm can be driven by the key via the one end in accordance with key depression, for pivotal motion about a support member. Further, the position of the other end of the arm can be adjusted within a range between an upper limit position and a lower limit position. When the position of the other end is set to the lower limit position, the arm is allowed to pivotally move about the support member in accordance with key depression, but when the position of the other end is set to the upper limit position, the other end cannot come into contact with the support member, so that no pivotal motion of the arm about the support member occurs. Thus, the weight of key touch feeling can be changed according to a position set for the other end of the arm. 
   In general, from the viewpoint of realizing expressive performance by a keyboard apparatus, it is considered desirable that an inertial force acts relatively lightly during strong key depression, i.e. when a key is quickly depressed, and acts relatively heavily during weak key depression, i.e. when a key is slowly depressed. However, in Japanese Laid-Open Utility Model Publication (Kokai) No. H02-64992, the key is always disengaged from the arm at a predetermined position in the key depression stroke, so that the same load is applied to the key in the same range of the key stroke irrespective of the intensity of the key depression. Further, in Japanese Patent No. 3221283, since the driving part of the key and the driven part of the arm are constantly held in engagement with each other, the same load is applied to the key in the same range of the key stroke irrespective of the intensity of key depression. 
   Therefore, these conventional keyboard apparatuses leave room for improvement in enhancement of key touch feeling in consideration of key depression intensity. 
   In Japanese Patent Publication (Kokoku) No. H01-47798, one end of the arm is constantly held in contact with the associated key, and besides, the arm also has mass in other parts than the weight. For this reason, even when the other end of the arm is at the upper limit position and the arm is kept from contact with the support member, the arm moves along with the key, and hence not a little inertial force generated by the motion of the arm is constantly applied to the key. Therefore, there is a limit to a setting for making key touch feeling light, and there still remains room for further improvement in changing key touch feeling distinctly and over a wide range. 
   SUMMARY OF THE INVENTION 
   It is a first object of the present invention to provide a keyboard apparatus which is capable of enhancing key touch feeling. 
   It is a second object of the present invention to provide a keyboard apparatus which allows switching of impartment/non-impartment of an inertial force to keys and adjustment of the inertial force to be imparted, thereby making it possible to change key touch feeling distinctly and over a wide range. 
   To attain the above first object, in a first aspect of the present invention, there is provided a keyboard apparatus comprising a support member, a plurality of keys that are supported by the support member, for key depressing operations, and an arm that is driven by an associated one of the keys via engagement with the associated key to move in a key depressing direction to thereby impart an inertial force to the associated key when the key is depressed, wherein the associated key is disposed for driving engagement with the arm such that a state of engagement between the associated key and the arm suddenly changes as a depressing velocity of the key changes across a predetermined key depressing velocity, such that when the depressing velocity of the key is higher than the predetermined key depressing velocity, the arm hardly moves in the key depressing direction, and when the depressing velocity is not higher than the predetermined key depressing velocity, the arm moves in the key depressing direction. 
   With the arrangement of the first aspect of the present invention, it is possible to make the touch feeling lighter in strong key depression than in weak key depression, thereby enhancing key touch feeling. 
   Preferably, the arm is movable in the key depressing direction and a predetermined direction different from the key depressing direction, and the associated key is disposed for driving engagement with the arm such that as the depressing velocity of the key is higher, motion of the arm in the predetermined direction has a higher priority over motion of the arm in the key depressing direction. 
   Preferably, wherein the driving engagement of the associated key with the arm is set such that driving of the key by the arm terminates during a depressing stroke of the key. 
   More preferably, the keyboard apparatus comprises a pivotal member that has one part thereof supported by the support member, and another part thereof pivotally movable about the one part, the other part having a pivot, and the arm and the pivotal member are disposed relative to each other such that the arm is pivotally movable about the pivot of the other part of the pivotal member, and the motion of the arm in the predetermined direction is realized by pivotal motion of the other part of the pivotal member about the one part. 
   More preferably, the keyboard apparatus comprises a biasing device that biases the arm in an opposite direction to the predetermined direction, and a restricting device that defines an initial position of the arm in the predetermined direction. 
   To attain the above first object, in a second aspect of the present invention, there is provided a keyboard apparatus comprising a support member, a plurality of keys that are supported by the support member, for key depressing operations, and an arm that is driven by an associated one of the keys to move in a key depressing direction to thereby impart an inertial force to the associated key when the key is depressed, wherein the associated key is disposed for driving engagement with the arm such that when a depressing velocity of the key is higher, an amount of motion of the arm in the key depressing direction is smaller than when the depressing velocity of the key is lower. 
   With the arrangement of the second aspect of the present invention, it is possible to make the touch feeling lighter in the strong key depression than in the weak key depression, thereby enhancing key touch feeling. 
   To attain the above first object, in a third aspect of the present invention, there is provided a keyboard apparatus comprising a support member, a plurality of keys that each have a driving part and are supported by the support member, for key depressing operations, an arm that has a driven part driven by the driving part of an associated one of the keys via engagement with the driving part of the associated key, the arm being movable in a key depressing direction by a key depressing force transmitted from the associated key through a frictional force generated by the engagement between the driven part and the driving part of the associated key when the driven part is driven by the driving part, to thereby impart an inertial force to the associated key when the key is depressed, wherein the associated key is disposed for driving engagement with the arm such that when the frictional force increases, the frictional force is relieved. 
   With the arrangement of the third aspect of the present invention, when the frictional force is relieved, the key depressing force transmitted from the key to the arm associated therewith is reduced. Therefore, e.g. by facilitating the escape of the frictional force in the strong key depression rather than in the weak key depression, it is possible to make the touch feeling lighter in the strong key depression than in the weak key depression. 
   Preferably, the associated key is disposed for driving engagement with the arm such that when the key depressing force transmitted from the associated key to the arm is not larger than a predetermined force, the engagement between the driven part and the driving part causes a static frictional state therebetween, whereas when the key depressing force transmitted from the associated key to the arm is not smaller than the predetermined force, the engagement between the driven part and the driving part causes a dynamic frictional state therebetween, and the frictional force is relieved when the static frictional state caused by the engagement between the driven part and the driving part is changed into the dynamic frictional state during an increase in the frictional force. 
   More preferably, the arm is movable in the key depressing direction and a predetermined direction different from the key depressing direction, and the associated key is disposed for driving engagement with the arm such that when the engagement between the driven part and the driving part causes the static frictional state, the arm mainly moves in the key depressing direction, whereas when the engagement between the driven part and the driving part causes the dynamic frictional state, the arm moves in the predetermined direction and hardly moves in the key depressing direction. 
   Further preferably, at least one of the driving part of the associated key and the driven part of the arm has a sloping surface part which is not parallel to the key depressing direction and the predetermined direction different from the key depressing direction, and the associated key is disposed for driving engagement with the arm such that the key depressing force is distributed in the key depressing direction and the predetermined direction according to an inclination angle of the sloping surface part, whereby the arm is made movable in the key depressing direction and the predetermined direction. 
   To attain the above second object, in a fourth aspect of the present invention, there is provided a keyboard apparatus comprising a support member, a plurality of keys that each have a driving part and are supported by the support member, for key depressing operations within a pivotal range thereof from a key-released state to a key-depressed state, a key return device that constantly operates to return an associated one of the keys toward the key-released state within the pivotal range of the associated key, an arm that has a driven part driven by the driving part of the associated key via engagement with the driving part of the associated key, the arm being pivotally moved when the driven part is driven by the driving part of the associated key, to thereby impart an inertial force to the associated key when the key is depressed, a switching device that switches between a first state where the driven part of the arm is driven by the driving part of the associated key during at least part of a forward key depression stroke, and a second state where the driven part of the arm is never driven by the driving part of the associated key through an entire key depression stroke, and an adjusting device that adjusts a degree of the engagement between the driven part and the driving part in the first state. 
   With the arrangement of the fourth aspect of the present invention, it is possible to switch the impartment/non-impartment of the inertial force to the key and adjust the inertial force to be imparted, thereby changing key touch feeling distinctly and over a wide range. 
   Preferably, the arm is displaceable in a predetermined direction containing a component perpendicular to a direction of pivotal motion of the arm, and the switching device displaces the arm in the predetermined direction to thereby switch between the first state and the second state. 
   More preferably, the arm comprises a plurality of the arms associated with respective ones of the plurality of keys, and the switching device collectively displaces the plurality of arms in the predetermined direction. 
   Preferably, the arm is displaceable in a predetermined direction containing a component perpendicular to a direction of pivotal motion of the arm, and the adjusting device adjusts the degree of the engagement between the driven part and the driving part in the first state by displacing the arm in the predetermined direction. 
   Preferably, the associated key is disposed for driving engagement with the arm such that in the first state, driving of the driven part by the driving part terminates halfway during the forward key depression stroke of the associated key, and timing in which the driving of the driven part by the driving part terminates during the forward key stroke is changed by the adjusting device adjusting the degree of the engagement between the driven part and the driving part. 
   Preferably, the arm comprises a plurality of the arms associated with respective ones of the plurality of keys, and the adjusting device is provided for each of the arms, for adjustment of the degree of the engagement between the driven part of the arm and the driving part of an associated one of the keys. 
   More preferably, the keyboard apparatus comprises a pivotal member that has one part thereof supported by the support member, and another part thereof pivotally movable about the one part, the other part having a pivot, and the arm and the pivotal member are disposed relative to each other such that the arm is pivotally movable about the pivot of the other part of the pivotal member, and the motion of the arm in the predetermined direction is realized by pivotal motion of the other part of the pivotal member about the one part. 
   Preferably, the keyboard apparatus comprises a return biasing device that is disposed for contact with an associated one of the keys in the key-depressed state to thereby set a key depression end position of the associated key, and wherein when the return biasing device is in contact with the associated key, the return biasing device biases the associated key toward the key-released state. 
   The above and other objects, features, and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a-keyboard apparatus according to a first embodiment of the present invention; 
       FIG. 2  is a fragmentary plan view of the keyboard apparatus; 
       FIG. 3  is a side view of an initial position adjusting mechanism appearing in  FIG. 1 ; 
       FIGS. 4A and 4B  are front views of essential parts and elements of the initial position adjusting mechanism in  FIG. 3 , in which: 
       FIG. 4A  shows a collective adjustment part; and 
       FIG. 4B  shows an individual adjustment part; 
       FIGS. 5A to 5D  are side views of the keyboard apparatus in a state where a key is weakly depressed in an “acoustic piano setting”, in which: 
       FIG. 5A  shows a non-key-depressed state; 
       FIG. 5B  shows a state where a weight of a hammer body has approached the lower surface of a key body; 
       FIG. 5C  shows a state where a pivot arm has pivotally moved in a counterclockwise direction as viewed in the figure; and 
       FIG. 5D  shows a state where the key body has returned to its initial position; 
       FIGS. 6A to 6M  are schematic views showing the relationship between a key depressing force, a vertical resisting force, and a frictional force in a state where the key is strongly depressed in the “acoustic piano setting”, in which: 
       FIGS. 6A ,  6 D,  6 G,  6 J, and  6 M shows changes with time in interaction between the key body and the hammer body; 
       FIGS. 6B ,  6 E,  6 H, and  6 K correspond to  FIGS. 6A ,  6 D,  6 G, and  6 J, respectively, and show the relationship between the vertical resisting force and the frictional force which are generated by a sloping surface part against the key depressing force; and 
       FIGS. 6C ,  6 F,  6 I, and  6 L correspond to  FIGS. 6A ,  6 D,  6 G, and  6 J, respectively, and show-the relationship between horizontal component forces and vertical component forces, which are applied to the sloping surface part in response to the vertical resisting force and the frictional force; 
       FIGS. 7A to 7D  are side views of the keyboard apparatus in a state where the key is strongly depressed in the “acoustic piano setting”, in which: 
       FIG. 7A  shows a non-key-depressed state; 
       FIG. 7B  shows a state in a stage well before termination of key depression; 
       FIG. 7C  shows a key depression end state of the key body; and 
       FIG. 7D  shows s state where the key body has returned to its initial position; 
       FIGS. 8A to 8D  are side views of the keyboard apparatus in an “organ setting”, in which: 
       FIG. 8A  shows a non-key-depressed state; 
       FIG. 8B  shows a state in a stage well before termination of key depression; 
       FIG. 8C  shows a key depression end state of the key body; and 
       FIG. 8D  shows a state where the key body has returned to the non-key-depressed state position; 
       FIGS. 9A to 9D  are schematic views showing a driving part and a driven part according to a variation  1  of the first embodiment, in which: 
       FIG. 9A  shows a static frictional state between the driving part and the driven part; 
       FIG. 9B  shows a static frictional state between the driving part and the driven part; 
       FIG. 9C  shows a dynamic frictional state between the driving part and the driven part; and 
       FIG. 9D  shows a state where the driving part has been disengaged from the driven part; 
       FIGS. 10A to 10H  are schematic views showing a driving part and a driven part according to a variation  2  of the first embodiment, in which: 
       FIG. 10A  shows an initial state in key depression; 
       FIG. 10B  shows a limit state where a moment MA can be barely balanced with a moment MB; 
       FIG. 10C  shows a state where the moment MA has exceeded the moment MB; and 
       FIG. 10D  shows a state where the driving part has been disengaged from a roller; 
       FIGS. 10E to 10H  are schematic views showing a driving part and a driven part according to a variation  3  of the first embodiment, in which: 
       FIG. 10E  shows an initial state in key depression; 
       FIG. 10F  shows a limit state where a moment MD can be barely balanced with a moment MC; 
       FIG. 10G  shows a state where the moment MD has exceeded the moment MC; and 
       FIG. 10H  shows a state where the driving part has been disengaged from the driven part; 
       FIGS. 11A to 11D  are schematic views showing a driving part and a driven part according to a variation  4  of the first embodiment, in which: 
       FIG. 11A  shows an initial state in key depression; 
       FIG. 11B  shows a key depression end state; 
       FIG. 11C  shows a key-released state; and 
       FIG. 11D  shows a further variation of the present variation; 
       FIG. 12A  is a perspective view showing essential parts of a moving mechanism for moving a hammer body in a longitudinal direction according to a variation  5  of the first embodiment; 
       FIG. 12B  is a schematic view showing essential parts of a moving mechanism for moving a hammer body in the longitudinal direction according to another variation; 
       FIGS. 12C and 12D  are side views showing examples of driven parts according to still other variations; 
       FIG. 13  is a side view of a keyboard apparatus according to a second embodiment of the present invention; 
       FIGS. 14A to 14C  are views showing component parts and elements of the keyboard apparatus in  FIG. 13 , in which: 
       FIG. 14A  is a side view showing details of an initial position adjusting mechanism of the keyboard apparatus according to the second embodiment; 
       FIG. 14B  is a perspective view of a driven part; and 
       FIG. 14C  is a schematic view showing the driven part and a hammer driving part in side view; and 
       FIG. 15  is a side view of a keyboard apparatus according to a third embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will now be described in detail with reference to the drawings showing preferred embodiments thereof. 
     FIG. 1  is a side view of a keyboard apparatus according to a first embodiment of the present invention. The keyboard apparatus of the present embodiment has a chassis  1  on which are supported key bodies  10  (a white key is shown in  FIG. 1  by way of example) to be depressed, hammer bodies  20  each for applying a moderate inertial force to a key body  10  associated therewith during key depression, and so forth, such that they can perform vertical swinging motion. Hereafter, the free end side (right side as viewed in  FIG. 1 ) of the key body  10  will be referred to as “the front”. 
   The key body  10  has a rear end part thereof supported such that the key body  10  can perform vertical pivotal motion about a key pivot  2 . The key body  10  has a weight  11  provided on a rearmost part thereof rearward of the key pivot  2 , and the weight  11  constantly urges, due to its own weight, the key body  10  in a counterclockwise direction as viewed in  FIG. 1  (i.e. in the opposite direction to the key depressing direction). A stopper contact part  13  extends downward from a lower part of the front end of the key body  10 . A hammer driving part  12  for driving the hammer body  20  extends downward from a lower part of the key body  10  at a location slightly rearward of the stopper contact part  13 . The lower end of the hammer driving part  12  is formed in an arcuate shape in cross section (see e.g.  FIG. 6A ). 
   An upper limit stopper  3  and a key-on switch  4  formed of an elastic material are disposed at respective locations on the chassis  1  corresponding to the stopper contact part  13  of the key body  10 . The key-on switch  4  may be implemented by an optical switch for detecting light. In a non-key-depressed state (key-released state), the stopper contact part  13  is held in contact with the upper limit stopper  3  due to the weight of the weight  11 , to thereby define a non-depressed position (i.e. a key stroke initial position) of the key body  10  as shown in  FIG. 1 . On the other hand, during key depression, the stopper contact part  13  is brought into contact with the key-on switch  4  by full depression of the key body  10 , to thereby define a key stroke end position of the key body  10 . At this time, the key depression is detected by the key-on switch  4 . It should be noted that a lower limit stopper may be provided on the chassis  1  so as to prevent the key-on switch  4  from being crushed. 
   The hammer bodies  20  are provided in a one-to-one correspondence with the key bodies  10 , and each of the hammer bodies  20  is supported such that it can perform vertical pivotal motion about an upper pivot  35  of a pivot arm  33 , described in detail hereinafter. The hammer body  20  has a weight  21  disposed on a rearmost end part thereof, and most of the mass of the hammer body  20  is concentrated on the weight  21 . The weight  21  constantly urges, due to its own weight, the hammer body  20  in the counterclockwise direction as viewed in  FIG. 1 . The hammer body  20  has a foremost end part thereof formed with a sloping surface part  22  facing obliquely forward and upward. As described hereinafter, this sloping surface part  22  functions as a driven part driven by the hammer driving part  12  of the key body  10 . 
   A hammer lower limit stopper  5  is provided on the chassis  1 , at a location approximately corresponding to the weight  21  of the hammer body  20 . In predetermined states, described hereinafter, including the non-key-depressed state, a free end part (rearmost end) of the hammer body  20  is held in contact with the hammer lower limit stopper  5  due to the weight of the weight  21 , to thereby define a pivotal stroke initial position of the hammer body  20  as shown in  FIG. 1 . 
   As described in detail hereinafter, due to engagement of the hammer driving part  12  of the key body  10  with the sloping surface part  22  of the hammer body  20 , the hammer body  20  pivotally moves in a key depressing direction (i.e. a clockwise direction as viewed in FIG.  1 ) according to depression of the associated key body  10 . The engagement relationship between the hammer driving part  12  and the sloping surface part  22  can be changed by an initial position adjusting mechanism AM 1 , described in detail hereinafter, which makes it possible to change key touch feeling. 
     FIG. 2  is a fragmentary plan view of the keyboard apparatus of the present embodiment.  FIG. 3  is a side view of the initial position adjusting mechanism AM 1 .  FIG. 2  shows the arrangement of the keyboard apparatus corresponding to a predetermined number of octaves (two octaves in the present embodiment). 
   As shown in  FIGS. 1 and 2 , a lower pivot  34  is fixedly disposed on the chassis, and the pivot arm  33  pivotally moves about the lower pivot  34  in the clockwise and counterclockwise directions as viewed in  FIG. 1 . A spring engaging part  31  is disposed on the chassis  1  at a location forward of the pivot arm  33 , and a front part of the pivot arm  33  and the spring engaging part  31  are connected to each other by a spring  32 . The pivot arm  33  and the spring  32  are provided in a one-to-one correspondence with each key body  10 . The spring  32  constantly pulls the pivot arm  33  in the clockwise direction as viewed in  FIG. 1 . In the present embodiment, only one spring engaging part  31  is commonly provided for the two-octave key bodies  10 , but separate spring engaging parts  31  may be provided for the respective key bodies  10 . 
   The initial position adjusting mechanism AM 1  is disposed on the chassis  1  at a location rearward of the pivot arm  33 . A thread  36  low in resilience has one end thereof attached to a rear part of the pivot arm  33 , and the other end thereof connected to a part (described hereinafter) of the initial position adjusting mechanism AM 1 . The initial position adjusting mechanism AM 1  is commonly provided for the two-octave key bodies  10 . The thread  36  is provided for each of the key bodies  10 . 
   Although in the present embodiment, the initial position adjusting mechanism AM 1  and the spring engaging part  31  are provided for the two-octave key bodies  10 , this is not limitative, but they may be provided for every three or more key bodies  10 , or commonly provided for all the key bodies  10 . 
   The initial position adjusting mechanism AM 1  is comprised of slide bases  37  ( 37 L and  37 R), an individual adjustment part  38 , connecting members  39  ( 39 L and  39 R), and collective adjustment parts  40  ( 40 L and  40 R). As shown in  FIG. 2 , the slide bases  37 L and  37 R, the connecting members  39 L and  39 R, and the collective adjustment parts  40 L and  40 R are symmetrically arranged on the respective left and right sides of the two-octave key bodies  10 , and each pair on the opposite sides are identical in construction. Hereafter, when it is not required to distinguish between the left and right parts, the characters “L” and “R” are omitted from the reference numerals, and the parts are simply referred to as the slide base(s)  37 , the connecting member(s)  39 , and the collective adjustment part(s)  40 , respectively. 
     FIG. 4A  is a front view of the collective adjustment part  40 L, and  FIG. 4B  a front view of the individual adjustment part  38 . The initial position adjusting mechanism AM 1  is symmetrical in construction, and hence in the following, a description will be basically given of the left side in  FIG. 2 . 
   As shown in  FIGS. 3 and 4A , the collective adjustment part  40 L is comprised of a fixed member  46 L having an L-shape in side view, and a collective adjustment slide member  45 L supported on the fixed member  46 L in a manner slidable forward and rearward. The fixed member  46  has an adjusting screw  48  mounted through a rear part thereof, and the position of the collective adjustment slide member  45  relative to the fixed member  46  in a longitudinal direction (a front-rear direction) can be adjusted by screwing in and out the adjusting screw  48 . Further, the collective adjustment slide member  45  can be fixed to the fixed member  46  by a fixing screw  47 . The fixed member  46  has a C channel-shaped guide member  82  embedded therein. A nut  81  is internally mounted in the guide member  82 , and has a lower end of the fixing screw  47  screwed therein. 
   On the other hand, as shown in  FIGS. 3 and 4B , the individual adjustment part  38  is comprised of a common slide member  42  having an L-shape in side view, and individual slide members  41 . The common slide member  42  is commonly provided for the two-octave key bodies  10 , while the individual slide members  41  are provided in a one-to-one correspondence with the key bodies  10 . 
   The common slide member  42  is bridged between the slide bases  37 L and  37 R. The slide base  37 L ( 37 R) is formed therein with a guide groove  37 La ( 37 Ra) having a generally C-shaped cross-section, and a portion of the common slide member  42  associated with the guide groove  37 La ( 37 Ra) is formed in a shape fittable in the guide groove  37 La ( 37 Ra). Thus, the common slide member  42  is allowed to slide along the guide grooves  37 La and  37 Ra on the slide bases  37 L and  37 R in the longitudinal direction. Further, the individual slide members  41  are each allowed to slide on the common slide member  42  in the longitudinal direction. 
   The common slide member  42  has adjusting screws  44  mounted through a rear part thereof, and the position of each of the respective associated individual slide members  41  relative to the common slide member  42  in the longitudinal direction can be adjusted by screwing in and out the adjusting screw  44 . Further, each of the individual slide members  41  can be fixed to the common slide member  42  by an associated fixing screw  43 . The common slide member  42  has C channel-shaped guide members  84  embedded therein. A nut  83  is internally mounted in each of the guide members  84 , and has a lower end of the associated fixing screw  43  screwed therein. 
   As shown in  FIGS. 2 and 3 , the front end of the collective adjustment slide member  45 L ( 45 R) and a corresponding portion of the rear end of the common slide member  42  are connected to each other by the connecting member  39 L ( 39 R). The connecting member  39  is formed of a material, such as a metal or a resin, which is less elastically-deformable than rubber or the like, or has no elastically-deformable property. Accordingly, the collective adjustment slide member  45  and the common slide member  42  connected thereto by the connecting member  39  are slid in unison for key touch feeling adjustment. The thread  36  is connected to the front end of an associated one of the individual slide members  41 . 
   The pivot arm  33  is constantly pulled by the associated spring  32  in the clockwise direction as viewed in  FIG. 1 , as described hereinabove, so that in the non-key-depressed state, the position or posture of the pivot arm  33  is maintained with the thread  36  held in a tensed (stretched) state. Therefore, insofar as the non-key-depressed state is concerned, the position of the pivot arm  33  in the direction of pivotal motion thereof is determined by the position of the associated individual slide member  41 , and the position of the associated hammer body  20  in the longitudinal direction is also determined at the same time. The positions of the pivot arm  33  and the hammer body  20  in the non-key-depressed state are also simply referred to as the “initial position(s)”. 
   With this arrangement, the initial position of each of the hammer bodies  20  is adjusted by “collective adjustment” and/or “individual adjustment” by the initial position adjusting mechanism AM 1 . 
   First, the collective adjustment will be described with reference to  FIG. 3 . The fixing screw  47  is loosened and the collective adjustment slide member  45  is brought into contact with the front end of the adjusting screw  48 . In this state, the position of the adjusting screw  48  is adjusted to slide the collective adjustment slide member  45  on the fixed member  46 . As the collective adjustment slide member  45  is slid, the connecting members  39  and the individual adjustment part  38  are slid. When the collective adjustment slide member  45  is moved to a desired position, the fixing screw  47  is screwed to fix the collective adjustment slide member  45  to the fixed member  46 . Thus, the initial positions of the respective hammer bodies  20  associated with the two-octave key bodies  10  can be collectively adjusted. 
   On the other hand, the individual adjustment is performed as follows: As in the relationship between the fixed member  46  and the collective adjustment slide member  45 , a fixing screw  43  associated with a hammer body  20  to be adjusted is loosened and the associated individual adjustment slide member  41  is brought into contact with the front end of the associated adjusting screw  44 . In this state, the position of the adjusting screw  44  is adjusted to slide the individual adjustment slide member  41  on the common slide member  42 . When the individual adjustment slide member  41  is moved to a desired position, the fixing screw  43  is screwed to fix the individual adjustment slide member  41  to the common slide member  42 . Thus, the initial positions of the hammer bodies  20  associated with the respective key bodies  10  can be individually adjusted. 
   Next, a description will be given of the operations of a key body  10  and that of the associated hammer body  20 . The operations of these members vary not only depending on a key touch style, i.e. key depressing velocity or key depression intensity, but also depending on the setting of the initial position of the hammer body  20 . 
   The setting of the position of the hammer body  20  in the longitudinal direction is roughly classified into two types, i.e. one setting (hereinafter referred to as “the acoustic piano setting”) in which the driving part  12  of the key body  10  is engaged with the sloping surface part  22  of the hammer body  20  (first state), as shown in  FIG. 1 , during at least a part of the key depression stroke and e.g. in the non-key-depressed state, and another setting (hereinafter referred to as “the organ setting”) in which the driving part  12  and the hammer body  20  are constantly kept apart from each other without ever being engaged with each other during the entire key depression stroke (second state), as described hereinafter with reference to  FIGS. 8A to 8D . In the “acoustic piano setting”, the initial position of the hammer body  20  can be adjusted in a continuous or stepless manner. Insofar as the engagement state of the driving part  12  and the sloping surface part  22  is concerned, an intermediate state between the organ setting and the acoustic piano setting can be set as described hereinafter. 
     FIGS. 5A to 5D  are side views of the keyboard apparatus in the case where slow key depression (hereinafter referred to as “the weak key touch”) is performed, which show changes with time in the operations of the key body  10  and the hammer body  20 .  FIGS. 6A to 6M  are schematic views showing the relationship between a key depressing force, a vertical resisting force, and a frictional force in “the acoustic piano setting” and in the weak key touch.  FIGS. 7A to 7D  are side views of the keyboard apparatus in the case where quick key depression (hereinafter referred to as “the strong key touch”) is performed, which show changes with time in the operations of the key body  10  and the hammer body  20 . 
   Now, taking an acoustic piano as an example, the “weak key touch” is a key touch style corresponding to key depression intensities ranging from a very weak key depression intensity in which a hammer barely strikes the associated string to a relatively weak key depression intensity, and the “strong key touch” is a key touch style much stronger than the weak key touch and corresponding to key depression intensities ranging from a key depression intensity for normal sounding to a key depression intensity for strong sounding. 
   First, the weak key touch will be described. In the non-key-depressed state shown in  FIG. 5A , the hammer driving part  12  of the key body  10  is in contact with the sloping surface part  22  of the hammer body  20 , and therefore, as the key body  10  is slowly depressed, the hammer driving part  12  presses the sloping surface part  22  downward, whereby the hammer body  20  pivotally moves in unison with the motion of the key body  10 . With this motion of the hammer body  20 , the weight  21  of the hammer body  20  approaches the lower surface of the key body  10  as shown in  FIG. 5B , with the hammer driving part  12  and the sloping surface part  22  being held in contact at a contact point P (see e.g.  FIG. 6A ). Therefore, during this time period, the hammer driving part  12  and the sloping surface part  22  are engaged with each other in a static frictional state, so that they hardly slide relative to each other, and hence the pivot arm  33  hardly moves, either. 
   More specifically, since the key body  10  pivotally moves about the key pivot  2 , and the hammer body  20  about the upper pivot  35 , if the pivot arm  33  does not pivotally move at all, the position of the pivot  35  does not change, and therefore the position of the key body  10  (hammer driving part  12 ) corresponding to the contact point P in the non-key-depressed state and that of the hammer body  20  (sloping surface part  22 ) do not draw the same pivotal locus. In other words, the pivotal loci of the two positions corresponding to the contact point P about the key pivot  2  and the pivot  35  in the non-key-depressed state progressively become away from each other as the key body  10  and the hammer body  20  pivotally move. However, as long as the hammer driving part  12  and the sloping surface part  22  are engaged with each other in a static frictional state, the pivot  35  is shifted in the forward direction by an amount for accommodating the difference between the two pivotal loci so as to keep the hammer driving part  12  and the sloping surface part  22  engaged together at the same contact point P, even though the amount of the shift is slight. 
   In the normal key touch styles including the weak key touch and the strong key touch, the pivotal motion of the hammer body  20  in the forward direction is stopped during the key depression before the weight  21  of the hammer body  20  is brought into contact with the lower surface of the key body  10 . Therefore, in the present embodiment, there is not provided an upper limit stopper for abutment with the hammer body  20 . This simplifies the construction of the keyboard apparatus and contributes to reduction of the thickness of the entire keyboard apparatus. 
   As described in detail hereinafter, after stoppage of the forward pivotal motion of the hammer body  20 , the engagement between the hammer driving part  12  and the sloping surface part  22  changes into a dynamic frictional state and the pivot arm  33  pivotally moves in the counterclockwise direction as shown in  FIG. 5C , the upper pivot  35  provided in the upper part of the pivot arm  33  shifts rearward, and the hammer body  20  is also shifted rearward (in a predetermined direction) in unison with the motion of the upper pivot  35 . As a consequence, the hammer driving part  12  is disengaged from the sloping surface part  22 , whereby a static let-off feeling like that provided by an acoustic piano can be obtained. Further, the stopper contact part  13  comes into contact with the key-on switch  4 , whereby the key depression is detected, and the depression or forward stroke of the key body  10  is terminated. 
   After disengagement of the hammer driving part  12  from the sloping surface part  22 , the hammer body  20  quickly moves in the counterclockwise direction with the front end (lower edge of the sloping surface part  22 ) thereof sliding on the rear wall of the hammer driving part  12 , to bring the weight  21  into contact with the hammer lower limit stopper  5 . At this time point, the hammer body  20  stands still at a position shifted slightly rearward from its originally set initial position. At this time, since the mass of the hammer body  20  is not applied to the key body  10 , even if the key body  10  is continuously depressed, only the static load of the key body  10  is applied to the player&#39;s finger, so that the finger cannot be fatigued. 
   Thereafter, when released from the key depressing force, the key body  10  returns to its initial position as shown in  FIG. 5D . On this occasion, the key body  10  receives not only the weight of the weight  11 , but also an initial reaction force from the key-on switch  4 , so that the key body  10  can quickly return to its initial position, which contributes to improvement of performance in repeated key striking. When the hammer driving part  12  returns to a position where its engagement with the sloping surface part  22  is allowed, by the return of the key body  10  to its initial position, the pivot arm  33  pivotally moves in the clockwise direction by the pulling or biasing force of the spring  32 , whereby the hammer body  20  also returns to its initial position. 
   Next, the interaction between the hammer driving part  12  and the sloping surface part  22  in the weak key touch will be described with reference to  FIGS. 6A to 6M . In  FIGS. 6A to 6L , the key depressing force is represented by F, the vertical resisting force by N′, and the frictional force by f′ .  FIGS. 6A ,  6 D,  6 G,  6 J, and  6 M show changes with time in the interaction between the hammer driving part  12  and the sloping surface part  22 .  FIGS. 6B ,  6 E,  6 H, and  6 K correspond to  FIGS. 6A ,  6 D,  6 G, and  6 J, respectively, and show the relationship between the vertical resisting force N′ and the frictional force f′ which are generated by the sloping surface part  22  against the key depressing force F.  FIGS. 6C ,  6 F,  6 I, and  6 L correspond to  FIGS. 6A ,  6 D,  6 G, and  6 J, respectively, and show the relationship between horizontal component forces and vertical component forces applied to the sloping surface part  22  in response to the vertical resisting force N′ and the frictional force f′. In  FIGS. 6A to 6M , the angle of the sloping surface part  22 , the shape of the hammer driving part  12 , and the magnitude of each force are shown in an exaggerated manner for purposes of ease of understanding. 
   In  FIGS. 6C ,  6 F,  6 I and  6 L, a horizontal component force and a vertical component force applied to the sloping surface part  22  in response to the vertical resisting force N′ are represented by Nx and Ny, respectively, and a horizontal component force and a vertical component force applied to the sloping surface part  22  in response to the frictional force f′ are represented by fx and fy, respectively.  FIGS. 6A to 6C  show the same state. Further,  FIGS. 6D to 6F ,  6 G to  6 I, and  6 J to  6 L show the respective same states. Hereafter, when the force groups in the respective states shown in  FIGS. 6A to 6C ,  6 D to  6 F,  6 G to  6 I, and  6 J to  6 L are to be distinguished from each other, parenthesized numbers ( 1 ) to ( 4 ) designating the respective states are added to the key depressing force F, the vertical resisting force N′ and its reaction force N, the frictional force f′ and its reaction force f, the horizontal component force Nx, the horizontal component force fx, the vertical component force Ny, and the vertical component force fy. For example, the key depressing force F and the frictional force f′ in  FIGS. 6A to 6C  are expressed as the key depressing force F( 1 ) and the frictional force f′ ( 1 ). 
   Hereafter, the term “friction” used in considering the interaction is intended to mean “sliding friction”. The hammer driving part  12  has an arcuate end, and hence, to be more precise, the hammer driving part  12  performs a rolling operation on the sloping surface part  22 , which produces slight rolling friction. However, this rolling friction has little effect on the key touch-related action, and therefore the rolling friction will be ignored in considering the interaction. 
   When the frictional state between the hammer driving part  12  and the sloping surface part  22  is compared between  FIGS. 6A ,  6 D,  6 G,  6 J, and  6 M,  FIGS. 6A and 6D  show a static frictional state, and  FIGS. 6G and 6J  show a dynamic frictional state. Therefore, a boundary separating between the static frictional state and the dynamic frictional state exists between  FIG. 6D  and  FIG. 6G .  FIGS. 6A and 6D  correspond to the respective states shown in  FIGS. 5A and 5B .  FIG. 6M  corresponds to the state shown in  FIG. 5C . 
   First, as shown in  FIG. 6A , in the initial stage of key depression, the downward key depressing force F( 1 ) is applied by the hammer driving part  12  to the sloping surface part  22  at the contact point P between the hammer driving part  12  and the sloping surface part  22 . The sloping surface part  22  is configured to cause moderate sliding friction, so that in the state shown in  FIG. 6A , the static frictional state is maintained. Therefore, the key depressing force F( 1 ) causes application of a vertical resisting force N′ ( 1 ) perpendicular to the sloping surface part  22  and a frictional force f′ ( 1 ) parallel to the same to the hammer driving part  12  at the contact point P (see  FIG. 6B ). 
   As shown in  FIG. 6C , a force N( 1 ) applied to the sloping surface part  22  (as a reaction force) in response to the vertical resisting force N′ ( 1 ) is divided at the contact point P into a horizontal component force Nx( 1 ) and a vertical component force Ny( 1 ) which are applied to the sloping surface part  22 . Further, a force f( 1 ) applied to the sloping surface part  22  (as a reaction force) in response to the frictional force f′ ( 1 ) is divided into a horizontal component force fx( 1 ) and a vertical component force fy( 1 ) which are applied to the sloping surface part  22 . At this time point, since the static frictional state is maintained, the horizontal component force Nx( 1 ) and the horizontal component force fx( 1 ) cancel each other. Consequently, almost no substantial forces in the longitudinal direction act on the hammer body  20 , and hence the hammer body  20  hardly moves in the longitudinal direction. On the other hand, in the vertical direction, the sum of the vertical component force Ny( 1 ) and the vertical component force fy( 1 ) (which sum is equal to the key depressing force F( 1 )) is applied to the sloping surface part  22 , which causes pivotal motion of the hammer body  20 . 
   The static frictional state is maintained until the hammer driving part  12  and the sloping surface part  22  enter the state shown in  FIGS. 6D to 6F . The relationship between the respective actions of the forces in the state in  FIGS. 6D to 6F  is the same that in the state in  FIGS. 6A to 6C . In the weak key touch, the player depresses the key body  10  such that the key body  10  pivotally moves at a substantially constant slow velocity, so that as long as the static frictional state is maintained, the key depressing force F is held substantially constant (i.e. F( 1 )=F( 2 )). However, since the inclination angle of the sloping surface part  22  progressively increases, the frictional force f′ progressively increases (f′ ( 1 )&lt;f′ ( 2 )). The state shown in  FIG. 6D  is a limit state where the static frictional state can barely be maintained, and here the frictional force f′ ( 2 ) is equal to the maximum frictional force depending on the static friction coefficient. 
   When the key body  10  is further depressed from the state shown in  FIG. 6D , since the frictional force f′ cannot exceed the maximum frictional force, the sliding frictional state between the hammer driving part  12  and the sloping surface part  22  suddenly changes from the static frictional state into the dynamic frictional state (see  FIG. 6G ). In short, sliding occurs. Actually, immediately after the sliding starts to occur, the static frictional state and the dynamic frictional state may alternately take place at short time intervals in a repeated manner. The dynamic friction coefficient is smaller than the static friction coefficient, and hence the frictional force f′ sharply decreases (i.e. f′( 3 )&lt;f′ ( 2 )) (see  FIG. 6H ). As a consequence, the horizontal component force fx( 3 ) becomes smaller than the horizontal component force Nx( 3 ) (see  FIG. 6I ). Therefore, after transition to the dynamic frictional state, the hammer body  20  receives a rearward biasing force, and the pivot arm  33  pivotally moves in the counterclockwise direction to shift the hammer body  20  rearward. 
   Further, after the hammer body  20  starts rearward motion, although the key depressing force F is larger than in the static frictional state, the vertical component force fy decreases relative to the horizontal component force Nx, and consequently the rearward motion has priority over the pivotal motion in the key depressing direction. Then, when the weight of the weight  21  comes to exceed the vertical component force fy, the hammer body  20  ceases to perform forward pivotal motion, and starts backward pivotal motion (see  FIGS. 6J to 6L ). Thereafter, when the hammer driving part  12  is disengaged from the sloping surface part  22 , the frictional state on the sloping surface part  22  disappears. Thus, the friction-based driving of the sloping surface part  22  by the hammer driving part  12  terminates, and as shown in  FIG. 6M , the key body  10  and the hammer body  20  enter the key depression end state shown in  FIG. 5C . 
   In this way, in the weak key touch, the driving of the sloping surface part  22  by the hammer driving part  12  continues until immediately before the end of the key depression stroke, and the load of the hammer body  20  is fully applied to the key body  10 , which makes touch feeling heavy, thereby enabling the player to easily play expressively e.g. by dragging. 
   Next, an operation in the “acoustic piano setting” and in the strong key touch will be described with reference to  FIGS. 7A to 7D . 
   First, when a key is quickly depressed in the non-key-depressed state shown in  FIG. 7A  (the same state as in  FIG. 5A ), the hammer driving part  12  and the sloping surface part  22  substantially skip the static frictional state to directly come into the dynamic frictional state. This direct transition occurs due to the force relief mechanism relieving the key depressing force in the longitudinal direction as well as the inertial action of the hummer body  20  having mass. Therefore, at the start of the pivotal motion of the key body  10 , the hammer driving part  12  and the sloping surface part  22  are brought into the same state as shown in  FIGS. 6J to 6L . Consequently, the hammer body  20  hardly performs pivotal motion in the key depressing direction, but pivotal motion of the pivot arm  33  in the counterclockwise direction causes the hammer body  20  to quickly shift rearward. 
   Then, at a much earlier stage than the end of the key depression, the hammer driving part  12  is disengaged from the sloping surface part  22 , as shown in  FIG. 7B , and the friction-based driving of the sloping surface part  22  by the hammer driving part  12  terminates, whereby, as shown in  FIG. 7C , the key body  10  and the hammer body  20  enter the same key depression end state as shown in  FIG. 5C . Therefore, in the forward key depression stroke, the load of the hammer body  20  is hardly applied to the key body  10 , which makes touch feeling light. Transition of the state shown in  FIGS. 7C to 7D  after cancellation of the key depressing force is the same as that shown in  FIGS. 5C to 5D . 
   In this way, in the strong key touch, the driving of the sloping surface part  22  by the hammer driving part  12  terminates at a very early stage of the key depression stroke, so that the touch feels lighter than in the weak key touch, which facilitates quick fingering and repeated key striking, thereby contributing to improvement of expressive playing ability. Further, both in the weak key touch and the strong key touch, during key depression continued after termination of the driving of the sloping surface part  22  by the hammer driving part  12 , the load of the hammer body  20  is not applied to the key body  10 , so that even in the case of generating a long tone, a weak force suffices to maintain the key-depressed state, which prevents the finger from being easily fatigued. 
   The amount of clockwise pivotal motion of the hammer body  20  or a clockwise pivotal force applied to the hammer body  20  in transition from the state in  FIG. 7A  to the state in  FIG. 7B  varies depending on the key depression intensity. Therefore, there is a possibility that the free end of the hammer body  20  does not separate from the hammer lower limit stopper  5  and the hammer body  20  is not pivotally moved at all. More specifically, when the key depressing velocity is high, the amount of pivotal motion of the hammer body  20  in the clockwise direction (key depressing direction) tends to be smaller than when the key depressing velocity is low. Further, the initial position of the hammer body  20  can be set such that when the key is depressed more quickly than at a predetermined key depressing velocity, the clockwise pivotal motion of the hammer body  20  does not occur at all. 
   Furthermore, in the “acoustic piano setting”, in both of the weak key touch and the strong key touch, the initial position of the hammer body  20  can be set by the initial position adjusting mechanism AM 1  to thereby change timing for terminating the driving of the sloping surface part  22  by the hammer driving part  12 , without changing the key depressing velocity. Thus, the hammer body  20  can perform different operations at the same key depressing velocity, which makes it possible to change key touch feeling as desired in accordance with a piece of music, a user&#39;s taste, and/or the tone color of tones to be generated. 
   To change key touch feeling, normally, the initial positions of the hammer bodies  20  are commonly adjusted over the whole range of pitches by carrying out the “collective adjustment” on a two-octave basis, whereby all the key bodies  10  can be easily set to provide the same key touch feeling. Further, key touch feeling of each key body  10  can be optimized by the “individual adjustment”. 
   Next, an operation in the “organ setting” will be described with reference to  FIGS. 8A to 8D .  FIGS. 8A to 8D  are side views of the keyboard apparatus in the “organ setting”, which show changes with time in the operations of the key body  10  and the hammer body  20 . In the “organ setting”, the weak key touch and the strong key touch are different in the velocity-of operation, but the same in the manner of change of the operations. 
   The “organ setting” is set by shifting the initial position of the hammer body  20  rearward by the “collective adjustment” to a position where the key body  10  is held out of contact or engagement with the hammer body  20  over the whole key depression stroke. It should be noted that a standard position of the collective adjustment slide member  45  corresponding to the “acoustic piano setting” and a position of the same corresponding to the “organ setting” may be set as preset positions, and marks or pins indicating the respective preset positions may be provided on the fixed member  46  so as to facilitate switching between the two positions. 
   First, in the non-key-depressed state, the hammer driving part  12  of the key body  10  and the front end of the hammer body  20  are apart from each other in the longitudinal direction, as shown in  FIG. 8A . Therefore, even when the key is depressed, the hammer driving part  12  cannot be engaged with the sloping surface part  22 , as shown in  FIGS. 8B and 8C , and hence the key body  10  alone is pivotally moved without receiving the load of the hammer body  20  at all. When the key depressing force is canceled, the key body  10  returns to the non-depressed position (see  FIG. 8D ). 
   As is apparent from the above description, the “organ setting” makes a touch on the key body  10  very light, so that the “organ setting” is suitable for playing organ pieces. Thus, the present embodiment makes it possible to easily achieve optimal key touch feeling for organ performance while allowing inertia impartment by the hammer body  20 . 
   The hammer driving part  12  and the sloping surface part  22  are each formed e.g. of a resin, and processing from selection of the material to surface finishing is carried out such that the desired frictional state between the surfaces of the two parts is obtained. Alternatively, a predetermined sheet, e.g. a non-woven fabric formed by application of pressure, may be affixed to the surfaces. The angle of the sloping surface part  22 , the shape of the front end of the hammer driving part  12 , and so forth, are related to the frictional state. Therefore, it is desirable that these factors are considered comprehensively or tested so as to achieve an optimal combination. 
   So far, the descriptions have been given by taking the key body  10  as a white key as an example, but a black key, not shown, is similar in construction to the key body  10 . The black key is also provided with parts, not shown, identical in construction to the spring engaging part  31 , the spring  32 , the pivot arm  33 , and the thread  36 , and a hammer body associated therewith is similar to the hammer body  20  in that its initial position can be adjusted. It should be noted that the same mechanism as that comprised of the initial position adjusting mechanism AM 1 , the spring engaging parts  31 , the springs  32 , the pivot arms  33 , and the threads  36  may be additionally provided for the black keys. 
   According to the present embodiment, in the “acoustic piano setting”, the state of engagement (frictional state) between the key body  10  and the hammer body  20  is suddenly changed as the key depression velocity is changed across a predetermined value. Consequently, in the weak key touch, that is, when the key is depressed at a velocity not higher than the predetermined key depressing velocity, the hammer driving part  12  and the sloping surface part  22  are engaged with each other while being held in the static frictional state over a wide range of the key depression stroke other than the latter half of the key depression stroke, whereas in the strong key touch, that is, when the key is depressed at a velocity higher than the predetermined key depressing velocity, the engagement in the static frictional state terminates at a very early stage of the key depression stroke. In the dynamic frictional state, the rearward motion of the hammer body  20  has priority over the pivotal motion of the same in the key depressing direction, so that the hammer body  20  is hardly moved in the key depressing direction. On the other hand, in the static frictional state, the hammer body  20  is mainly moved in the key depressing direction. Therefore, in the strong key touch, the load of the hammer body  20  applied to the key body  10  is smaller than in the weak key touch. The hammer body  20  is driven by the key body  10  via sliding friction generated between the hammer driving part  12  and the sloping surface part  22 , to impart an inertial force to the key body  10 . During the increase in the frictional force, the frictional state between the hammer driving part  12  and the sloping surface part  22  is suddenly changed from the static frictional state to the dynamic frictional state to relieve the frictional force, whereby the above described operation of the hammer body  20  dependent on the key depression intensity is realized. Thus, touch feeling in the strong key touch can be set to be lighter than that in the weak key touch. The inertial force imparted to the key body  10  by the hammer body  20  acts lightly in the strong key touch and heavily in the weak key touch, whereby key touch feeling required for carrying out expressive musical performance can be achieved. In this respect, key touch feeling of the present keyboard apparatus is not the same as that of a general acoustic piano, but if only the player gets accustomed to the touch that feels light only in the strong key touch, there is a possibility that key touch feeling is valued as more excellent than that of the acoustic piano. 
   Further, in the “acoustic piano setting”, the driving of the sloping surface part  22  of the hammer body  20 .by the hammer driving part  12  of the key body  10  terminates halfway during the key depression stroke, and hence the load of the hammer body  20  is not applied to the key body  10  at the end of the key depression. Therefore, even in the case of maintaining the key-depressed state, it is possible to minimize the fatigue of the finger. In the weak key touch, touch feeling becomes light as is the case with the operation after the state shown in  FIG. 5C . This enables impartment of the same let-off feeling as sensed in both strong touch and weak touch achieved in the acoustic piano, particularly in a grand piano. 
   Further, since the hammer body  20  pivotally moves about the upper pivot  35  of the pivot arm  33 , and the forward and rearward motion of the hammer body  20  is achieved by the pivotal motion of the pivot arm  33  about the lower pivot  34 , high durability of the turning and moving mechanisms of the hammer body  20  can be ensured. 
   Furthermore, since the position or posture of the pivot arm  33  is stabilized by the forward biasing force of the spring  32  and the tension of the thread  36 , the initial position of the pivot arm  33  can be stably maintained. 
   According to the present embodiment, the initial position of the hammer body  20  in the longitudinal direction can be adjusted by the initial position adjusting mechanism AM 1  to thereby switch between the roughly defined two settings, i.e. the “acoustic piano setting” and the “organ setting”, which makes it possible to easily realize key touch feelings of respective quite different keyboard apparatuses, i.e. an acoustic piano and an organ, by a single keyboard apparatus. In addition, in-the “acoustic piano setting”, the degree of engagement between the hammer driving part  12  and the sloping surface part  22  can be adjusted in a continuous or stepless manner by the initial position adjusting mechanism AM 1 , which makes it possible to change the timing for terminating the driving in a forward key depression stroke of the sloping surface part  22  by the hammer driving part  12  as desired. Therefore, it is possible to vary the manner of application of the inertial force to the key body  10  to thereby change key touch feeling the hammer driving part  12  distinctly and over a wide range. 
   Further, since the initial position adjusting mechanism AM 1  is capable of collectively adjusting two-octave hammer bodies  20 , key touch feelings of a plurality of keys can be collectively changed, thereby facilitating the operation of changing key touch feeling. Moreover, since the individual adjustment part  38  is provided, key touch feeling of each key can be adjusted individually, which is convenient in fine adjustment. 
   Although in the present embodiment, the initial position adjusting mechanisms AM 1  are provided on a two-octave basis, this is not limitative, but it is possible to provide an initial position adjusting mechanism AM 1  for each predetermined audio frequency range, thereby enabling collective adjustment of key touch feeling of keys in each predetermined audio frequency range so as to provide key touch feelings quite different from audio frequency range to audio frequency range. For example, an application can be considered in which in a single keyboard apparatus, key touch feelings corresponding to respective audio frequency ranges are made quite different from each other such that key touch feeling of a grand piano can be obtained in the low audio frequency range, and key touch feeling of an upright piano or an organ in the high audio frequency range. Further, key touch feeling in an intermediate state between a piano state and an organ state, which cannot be provided by the conventional keyboard apparatuses, can also be easily achieved. 
   Although in the present embodiment, a predetermined direction other than the direction of the pivotal motion of the hammer body  20 , in which the hammer body  20  is movable, is the rearward direction, this is not limitative. For the purpose of relieving the frictional force generated between the hammer driving part  12  and the sloping surface part  22 , the predetermined direction may be any direction that is different from the key depressing direction. Further, for the purpose of varying the engagement between the hammer driving part  12  and the sloping surface part  22 , the predetermined direction may be any direction containing a component vertical to the direction of the pivotal motion of the hammer body  20 . 
   Although in the initial position adjusting mechanism AM 1 , the “acoustic piano setting” and the “organ setting” are generally set by the collective adjustment part  40 , a mechanism for carrying out two-position switching between the two settings and a mechanism for changing the setting in a continuous or stepless manner may be provided together, in place of the collective adjustment part  40 . Alternatively, the initial position adjusting mechanism AM 1  may be configured such that the individual adjustment part  38  is used as a mechanism for changing the setting in a continuous or stepless manner, and apart from the individual adjustment part  38 , a mechanism for carrying out the two-position switching may be provided in place of the collective adjustment part  40 . 
   Although in the present embodiment, the collective adjustment part  40  is disposed rearward of the individual adjustment part  38 , the collective adjustment part  40  may be disposed forward of the individual adjustment part  38  in view of operability. The spring  32  may be replaced by any other suitable member, insofar as it is capable of biasing the pivot arm  33  forward. 
   Next, variations of the first embodiment will be described with reference to  FIGS. 9A to 12D . 
     FIGS. 9A to 9D  are schematic views of a driving part and a driven part according to a variation  1  of the first embodiment. In the first embodiment (the keyboard apparatus in  FIG. 1 ), the lower end of the hammer driving part  12  as the driving part is formed to have an arcuate shape in side view, and the sloping surface part  22  of the hammer body  20  as the driven part is formed as an even surface. In the variation  1 , the relationship in shape between the two parts is reversed such that the driving part  51  is formed to have a sloping surface and the driven part  52  is formed to have an arcuate shape in side view. 
   With this arrangement as well, the driving part  51  and the driven part  52  in engagement act in the same manner as in the first embodiment. More specifically, in states shown in  FIGS. 9A and 9B , the two parts are in the same static frictional state as that shown in  FIGS. 6A and 6D . In a state shown in  FIG. 9C , the two parts come into a dynamic frictional state as the hammer driving part  12  and the sloping surface part  22  do in  FIG. 6J , and then, as shown in  FIG. 9D , the driving part  51  is disengaged from the driven part  52  as the hammer driving part  12  is in  FIG. 6M . Therefore, it is possible to provide the same advantageous effects as provided by the first embodiment. 
     FIGS. 10A to 10D  are schematic views of a driving part and a driven part according to a variation  2  of the first embodiment. In the variation  2 , a cylindrical roller  55  as the driven part is rotatably held by a roller holding part  54   a  of a hammer body  54 . The driving part  53  has a lower end thereof formed in an arcuate shape in side view. 
   First, as shown in  FIG. 10A , in an early stage of key depression, a moment MA ( 1 ) in a clockwise direction as viewed in  FIG. 10A  acts on the roller  55  from the driving part  53 . On the other hand, in the hammer body  54 , the roller  55  is in a static frictional state with respect to the roller holding part  54   a  of the hammer body  54 , and a moment MB ( 1 ), which is generated by a frictional force in a counterclockwise direction as viewed in  FIG. 10A , acts on the roller  55 . At this time point, the moment MA ( 1 ) and the moment MB ( 1 ) are balanced with each other. Therefore, the roller  55  does not rotate, and the hammer body  54  itself pivotally moves as the hammer body  20  does in the state shown in  FIG. 6A . 
   Then, after the pivotal angle of the hammer body  54  changes and the moment MA ( 2 ) reaches a limit of the balance with the moment MB ( 2 ) (see  FIG. 10B ), the sliding frictional state between the roller  55  and the roller holding part  54   a  of the hammer body  54  suddenly changes from the static frictional state to a dynamic frictional state, and the moment MA ( 3 ) exceeds the moment MB ( 3 ) to cause clockwise rotation of the roller  55  (see  FIG. 10C ). As a consequence, the hammer body  54  shifts rearward as the hammer body  20  does in the state shown in  FIG. 6J , and then, as shown in  FIG. 10D , the driving part  53  is disengaged from the roller  55  as the hammer driving part  12  is disengaged from the hammer body  20  in  FIG. 6M . 
     FIGS. 10E to 10H  are schematic views of a driving part and a driven part according to a variation  3  of the first embodiment. In the variation  3 , a hammer body  58  is formed with a driven part  59  with a sloping surface similar to the sloping surface part  22  of the keyboard apparatus of the first embodiment, and a cylindrical roller  57  is rotatably held by a roller holding part  56   a  of the driving part  56 . 
   First, as shown in  FIG. 10E , in an early stage of key depression, a moment MD ( 1 ) in a clockwise direction as viewed in  FIG. 10E  acts on the roller  57  from the driving part  59 . On the other hand, in the driving part  56 , the roller  57  is in a static frictional state with respect to the roller holding part  56   a  of the driving part  56 , and a moment MC ( 1 ), which is generated by a frictional force in a counterclockwise direction as viewed in  FIG. 10E , acts on the roller  57  from the roller holding part  56   a . At this time point, the moment MD ( 1 ) and the moment MC ( 1 ) are balanced with each other. Therefore, the roller  57  does not rotate, and the hammer body  58  itself pivotally moves as the hammer body  20  does in the state shown in  FIG. 6A . 
   Then, after the pivotal angle of the hammer body  58  changes and the moment MD ( 2 ) reaches a limit of the balance with the moment MC ( 2 ) (see  FIG. 10F ), the sliding frictional state between the roller  57  and the roller holding part  56   a  suddenly changes from the static frictional state to a dynamic frictional state, and the moment MD ( 3 ) exceeds the moment MC ( 3 ) to cause clockwise rotation of the roller  57  (see  FIG. 10G ). As a consequence, the hammer body  58  shifts rearward as the hammer body  54  does in the state shown in  FIG. 10C , and then, as shown in  FIG. 10H , the driving part  56  is disengaged from the driven part  59  as the driving part  53  is disengaged from the roller  55  in  FIG. 10D . 
   In the variations  2  and  3  as well, in which the hammer body is driven not through friction directly generated between the key body and the hammer body, but through friction generated between the roller holding part of the hammer body or the key body and the roller, changes in the action of the frictional force are basically the same as those in the first embodiment. Therefore, the variations  2  and  3  can provide the same advantageous effects as provided by the first embodiment. 
   It should be noted that by providing both of the hammer body and the key body with a roller, the same function and actions can be achieved. 
     FIGS. 11A to 11C  are schematic views of a driving part and a driven part according to a variation  4  of the first embodiment. In the variation  4 , a driving part, which can be bent, is used. More specifically, the driving part  60  corresponding to the hammer driving part  12  is comprised of a base part  61 , and an arm part  62 , and is formed such that the arm part  62  can be bent only downward about a pivot  63 , as viewed in  FIGS. 11A to 11C , with respect to the base part  61 . Further, the driving part  60  is provided with a biasing member, not shown, for returning the arm part  62  to a state shown in  FIG. 11A . On the other hand, a hammer body  64  is formed with a driven part  65  with a sloping surface similar to the sloping surface part  22  of the keyboard apparatus of the first embodiment. 
   With the construction described above, the action in a forward stroke in which the driving part  60  drives the hammer body  64  is the same as that in the first embodiment. The operation starts from the initial state shown in  FIG. 11A  and proceeds to a key depression end state shown in  FIG. 11B  through sliding of the front end of the arm part  62  on the driven part  65 , and the pivotal motion and rearward shift of the hammer body  64 . 
   As is distinct from the first embodiment in which a key enters the key depression end state with the front end of the hammer body  20  held in contact with the rear wall of the hammer driving part  12 , according to the present variation  4 , in the key depression end state, the driving part  60  is positioned below the hammer body  64 , and the hammer body  64  need not be in contact with the driving part  60  but has already returned to its initial position. 
   On the other hand, when the key is released, the driving part  60  moves upward, and the arm part  62  is temporarily bent about the pivot  63 , as shown in  FIG. 11C , whereby the driving part  60  is allowed to move upward to a level above the hammer body  64  and easily return to its initial position. The variation  4  also ensures the same advantageous effects as provided by the first embodiment. 
   It should be noted that a pin  78  may be provided in a hammer body  77  in a suspended manner, as shown in  FIG. 11D , in place of the driven part  65  as the sloping surface, so as to be driven by the driving part  60 . Such a configuration in which a pin is used as a driven part can also be applied to the first embodiment and the variations  1  and  3 . Further, a configuration in which a bendable driving part is used as described above as the variation  4  by way of example is applicable to each of the driving parts in the first embodiment and the variations  1  to  3 . 
   Next, a description will be given of another configuration in which a moving mechanism moves a hammer body in the longitudinal direction as a variation  5  of the first embodiment. In the first embodiment, the forward or rearward shift of the hammer body  20  is realized by the pivotal motion of the pivot arm  33  about the lower pivot  34 , but other forms of moving mechanisms can be considered. 
     FIG. 12A  is a perspective view showing essential parts of a moving mechanism for moving a hammer body in the longitudinal direction, according to the variation  5  of the first embodiment. 
   A support member  69  is fixed to the chassis  1  in place of the pivot arm  33 . A hammer body  66  has a lower part formed with a suspending part  67  extending downward therefrom, and cylindrical pins  68  are projected laterally from the suspending part  67 . The suspending part  67  has a lower edge thereof formed in an arcuate shape in side view. The support member  69  is configured similarly to a sliding member shown in  FIG. 3  of Japanese Patent No. 3324384. More specifically, the support member  69  is formed therein with a U-shaped main guide groove  70  extending in the longitudinal direction, for guiding the suspending part  67 , and pin guide grooves  71  and  72  for guiding the pins  68  are formed in the respective left and right inner side surfaces of the main guide groove  70  and extend in the longitudinal direction. 
   The suspending part  67  of the hammer body  66  is fitted in the main guide groove  70  of the support member  69 , and the pins  68  are fitted in the pin guide grooves  71  and  72 . When the hammer body  66  receives a force acting in the key depressing direction, the arcuate suspending part  67  rolls in the main guide groove  70 , which causes pivotal motion of the hammer body  66 . On the other hand, when the hammer body  66  receives a force acting in the rearward direction, the suspending part  67  slides rearward along the main guide groove  70 , whereby the hammer body  66  shifts rearward. At this time, the pins  68  also slide along the pin guide grooves  71  and  72 , so that the hammer body  66  can smoothly move forward and rearward irrespective of a position where the hammer body  66  pivotally moves. In addition, since the pins  68  are fitted in the pin guide grooves  71  and  72 , it is possible to prevent the hammer body  66  from falling out from the support member  69  even when a shocking key touch is applied. 
   In the variation  5  as well, high durability of the turning and moving mechanisms of the hammer body can be ensured, and therefore it is possible to provide the same advantageous effects as provided by the first embodiment. 
   It should be noted that for the purpose of simplifying the construction of the moving mechanism for moving the hammer body in the longitudinal direction, it is possible to employ a configuration in which a hammer body  73  is placed on a cylindrical pivot  74  as shown in  FIG. 12B . 
   Although in each of the first embodiment and the variations  1 ,  3  and  4 , the driving part or the driven part is formed as having an even sloping surface, this is not limitative, but the shape of the sloping surface may be a concave sloping surface  75  shown in  FIG. 12C  or a convex sloping surface  76  shown in  FIG. 12D , for example. In this case, the horizontal component forces and vertical component forces applied to the driven part in a key depression stroke are not changed in a linear fashion, but can be changed in a desired fashion by adjusting the curvature of the curved surface, which makes it easier to further approximate key touch feeling to a desired one. 
     FIG. 13  is a side view of a keyboard apparatus according to a second embodiment of the present invention. The keyboard apparatus of the present embodiment has a chassis  112  on which are supported key bodies  110  (a white key is shown in  FIG. 13 ) to be depressed, hammer bodies  120  each for applying a moderate inertial force to a key body  110  associated therewith during key depression, and so forth, such that they can perform vertical swinging motion. Hereafter, the free end side (the right side as viewed in  FIG. 13 ) of the key body  110  will be referred to as “the front”. 
   The key body  110  is supported such that it can perform vertical pivotal motion about a key pivot P 1 . A return spring  113  is stretched at an uppermost location in the chassis  112  between an approximately longitudinally central part and a rear part of the key body  110 . A hammer driving part  111  for driving the hammer body  120  extends downward from a front lower part of the key body  110 . On the top of the chassis  112 , there is disposed a key-on switch  114 , and on the front part of the chassis  112 , there is provided a key guide  126 . Further, an upper limit setting stopper  125  is disposed on a rear upper part of the chassis  112 . 
   A lower pivot  134  is fixedly provided on the chassis  112 . Further, on the chassis  112 , there is attached a pivot arm  133  pivotally movable about the lower pivot  134  in the clockwise and counterclockwise directions as viewed in  FIG. 13 . The hammer bodies  120  are provided in a one-to-one correspondence with the key bodies  110 , and are supported such that they can perform vertical pivotal motion about respective associated upper pivots  135  of the pivot arms  133 . Each of the hammer bodies  120  has a driven part  121 , described in detail hereinafter, formed on a foremost end thereof. 
   A front side of the pivot arm  133  and a front part of the chassis  112  are connected to each other by a spring  132 . An initial position adjusting mechanism AM 2  is disposed on the chassis  112  at a location rearward of the pivot arm  133 . A thread  136  has one end thereof attached to a rear side of the top of the pivot arm  133 , and the other end thereof connected to a part (described hereinafter) of the initial position adjusting mechanism AM 2 . The spring  132 , the pivot arm  133 , and the thread  136  are provided in a one-to-one correspondence with the key bodies  10 . These members are different in positional relationship and shape from the spring  32 , the pivot arm  33 , and the thread  36  in the first embodiment, but are similar in function to them. 
     FIG. 14A  is a side view showing details of the arrangement of the initial position adjusting mechanism AM 2  of the keyboard apparatus of the present embodiment.  FIG. 14B  is a perspective view of the driven part  121 , and  FIG. 14C  is a side view schematically showing the driven part  121  and the hammer driving part  111 . 
   The initial position adjusting mechanism AM 2  includes a slide base  137 , a common slide member  138 , and an operating arm  140 . The slide base  137  is formed therein with guide grooves  137   a  similar to the guide grooves  37 La and  37 Ra (see  FIG. 3 ), and a lower portion of the common slide member  138  corresponding to the guide grooves  137   a  is formed in a shape fittable in the guide grooves  137   a . The guide grooves  137   a  extend along a direction substantially parallel with a line connecting between the initial position adjusting mechanism AM 2  and the top of the pivot arm  133  (i.e. substantially the same direction as the longitudinal direction of the thread  136 ), and hence the common slide member  138  is movable in this direction. 
   The operating arm  140  is allowed to pivotally move about a pivot  142  provided in the slide base  137  in clockwise and counterclockwise directions as viewed in  FIG. 14A . The operating arm  140  is formed therein with a slot  139  in which is fitted a pin  141  projecting from the common slide member  138 . The thread  136  is connected to the common slide member  138 . 
   The slide base  137  is disposed on each of the left and right sides of a group of key bodies  110  corresponding to a predetermined number of octaves. The left and right slide bases  137  are symmetrical. The common slide member  138  is bridged between the left and right slide bases  137 . The group of key bodies  110  corresponding to the predetermined number of octaves is provided with at least one operating arm  140 , i.e. one on one side thereof or two on the respective opposite sides thereof, for example. 
   With the construction described above, when the user pivotally moves the operating arm  140 , the common slide member  138  is moved via the slot  139  and the pin  141  in the direction set for movement along the slide bases  137 . As a consequence, the pivot arm  133  has its pivotal position set as the pivot arm  33  does in the first embodiment, so that the initial positions of the respective hammer bodies  120  associated with the key bodies  110  corresponding to the predetermined number of octaves can be collectively adjusted. 
   As shown in  FIG. 14B , the driven part  121  has a front end thereof provided with a cylindrical roller  123  such that the roller  123  can rotate about a rotational shaft  124 . Differently from the rollers  55  and  57  shown in  FIGS. 10A to 10H , the roller  123  is configured such that sliding friction during rotation is minimized. Further, as shown in  FIG. 14C , the driven part  121  is formed with a sloping surface part  122  similar to the sloping surface part  22  of the hammer body  20  in the first embodiment. The roller  123  is slightly projected vertically from a lower part of the sloping surface part  122 . 
   With the construction described above, when the driven part  121  is driven in the weak key touch by the hammer driving part  111 , the hammer driving part  111  and the sloping surface part  122  act relative to each other in the same manner as the hammer driving part  12  and the sloping surface part  22  in the first embodiment (see  FIGS. 6A to 6L ) up to a halfway point (i.e. until the hammer driving part  111  comes into contact with the roller  123 ). 
   However, when the hammer driving part  111  comes into contact with the roller  123 , the projection of the roller  123  from the lower part of the sloping surface part  122  causes a temporary increase in the key depression reaction force, or temporarily lowers the degree of reduction of the key depression reaction force. As a result, the same let-off feeling as obtained from the acoustic piano can be positively sensed. 
   Further, as is distinct from the first embodiment in which no upper limit stopper for the hammer body  20  is provided, in the present second embodiment, the upper limit setting stopper  125  is provided as mentioned above. In a normal key-depressed state, a rear end part  120   a  of the hammer body  120  is never brought into contact with the upper limit setting stopper  125 , but even when the pivotal motion end position of the hammer body  120  is shifted to an unexpected position due to aging (including changes in the frictional state) or an excessively rough key touch, a shock applied to the finger from the key body  110  is reduced by the upper limit setting stopper  125 . 
   The present embodiment can not only provide the same advantageous effects as provided by the first embodiment except those associated with individual adjustment of the initial position of each hammer body, but also further facilitate collective adjustment of the respective initial positions of the hammer bodies. Further, since the roller  123  is provided in the driven part  121 , the same let-off feeling as peculiarly sensed in the weak key touch on the acoustic piano can be clearly or positively realized. On the other hand, in the strong key touch, a driving force of the hammer driving part  111  is not transmitted to the roller  123 , but transmitted to the hammer body  120  in the initial stage of key depression, so that in this case as well, the same let-off feeling as sensed generally in the weak key touch on the acoustic piano can be realized. 
   Also in the second embodiment, it is desirable to provide a mechanism similar to the initial position adjusting mechanism AM 1  in the first embodiment so as to enable individual adjustment of the initial position of each hammer body. It should be noted that a weight having a function for returning the key body  110 , which is similar to the function of the weight  11  in the first embodiment, may be provided e.g. in the front part of the key body  110 . 
   Referring again to the first embodiment, the mechanism for moving the collective adjustment slide member  45  on the fixed member  46  may be implemented by the mechanism operated by the operating arm  140  in the second embodiment. Further, the roller  123  in the second embodiment may be employed in the first embodiment. 
   The mechanism for adjusting the initial positions of the hammer bodies is not limited to the mechanisms described in the first and second embodiments by way of example. Further, the operating method for adjustment is not limited to the manual one, but an electric/electromagnetic moving mechanism may be used. Furthermore, a thread take-up mechanism may be employed as a mechanism for holding the thread under tension like the initial position adjusting mechanism AM 1  and the initial position adjusting mechanism AM 2 . In this case, the initial position of each hammer body is adjusted based on a take-up amount. 
     FIG. 15  is a side view of a keyboard apparatus according to a third embodiment of the present invention. The third embodiment is basically distinguished from the first embodiment in that with key depression, a hammer body  220  corresponding to the hammer body  20  moves not rearward, but forward. Therefore, in addition to the hammer body  220 , a spring  232  as a compression spring and an initial position adjusting mechanism AM 3  are employed in place of the spring  32  as a tension spring and the initial position adjusting mechanism AM 1 , respectively. Further, as a member having the function for returning the key body  10 , a tension spring  245  is provided at the rear end of the key body  10  in place of the weight  11 . 
   At the foremost part of the hammer body  220 , there is formed an even sloping surface part  222  facing rearward and upward, and the sloping surface part  222  functions as a driven part driven by the hammer driving part  12  of the key body  10 . The front side of the pivot arm  33  and the spring engaging part  31  are connected to each other by the spring  232 . 
   The initial position adjusting mechanism AM 3  is comprised of a gear base  242  fixed to the chassis  1 , a gear  243  fixed to the gear base  242 , and a worm  244  in mesh with the gear  243 . The worm  244  is rotated by a motor  241 . The worm  244 , which is in mesh with the gear  243 , moves generally in the longitudinal direction while rotating. The stop position of the motor  241  is defined by a position sensor, not shown, which detects the forward and rearward motions of the worm  244 . 
   When the upper half part of the pivot arm  33  is pivotally biased rearward about the lower pivot  134  by the spring  232 , the front end of the worm  244  abuts against the rear wall of the pivot arm  33  to withstand the urging force of the spring  232 . This makes it possible to adjust the initial position of the pivot arm  33  by changing the position of the worm  244 . Further, when the hammer body  220  receives a force acting to move the same forward, the spring  232  contracts to allow forward pivotal motion of the pivot arm  33 . 
   Operations during key depression are the same as those in the first embodiment except that the hammer body  220  shifts forward. Further, by adjusting the position of the worm  244  of the initial position adjusting mechanism AM 3 , the “organ setting” and the “acoustic piano setting” can be set in the same manner as set by the initial position adjusting mechanism AM 1 . 
   The present embodiment can provide the same advantageous effects as provided by the first embodiment, except those associated with individual adjustment of the initial position of each hammer body.