Abstract:
A mute piano is responsive to key movements and pedal movements so as to produce music data codes expressing the pitch of tones and pedal effect to be given to the tones in accordance with the MIDI protocols, and the damper pedal stroke is divided into a rest region, a half-pedal region and a damper-free region which are expressed by difference numerical ranges of data bytes of the musical data code: since the piano has its own individuality, the relation between the pedal position and the value of data bytes is to be calibrated; the controller of the mute piano enters a calibration mode, and optimizes the relation to the actual damper actions, thereby causing the music data code exactly to express the effect of the damper pedal to be given to the tones.

Description:
FIELD OF THE INVENTION 
     This invention relates to a musical instrument and, more particularly, to a keyboard musical instrument having a pedal system monitored with a pedal sensor or sensors for converting the movement of the pedal or pedals to an electric signal and a controlling system incorporated in the keyboard musical instrument. 
     DESCRIPTION OF THE RELATED ART 
     A mute piano is an example of the keyboard musical instrument of the type having a pedal system monitored with a pedal sensor or sensors. The mute piano is a combination of an acoustic piano and an electronic system. It is possible for a user sequentially to produce acoustic piano tones along a music passage. In other words, the user has the use of mute piano as an ordinary piano, and this usage is hereinafter referred to as “acoustic playing mode”. The mute piano is changeable from the acoustic playing mode to a mute mode. When the user changes the mute piano to the mute mode, the acoustic piano is prohibited from the production of acoustic piano tones. Instead, electronic tones are produced through the electronic system. 
     While the user is performing a music passage in the mute mode, the movements of the black and white keys and pedal are analyzed by the electronic system for producing the electronic tones. When the electronic system notices the user depress a black key and release a white key, the electronic system starts to produce the tone at the pitch assigned to the black key, and starts to decay the tone at the pitch assigned to the white key. When the electronic system notices the user step on a pedal, the electronic system gives the effect expressed by the pedal to the tone or tones. 
     One of the pedals is called as a “damper pedal”, and players frequently step on during their performances. The damper pedal is linked with a damper mechanism, and the damper mechanism makes the dampers spaced from the strings and brought into contact with the strings, again. The trajectory of dampers is broken down into three regions, which are hereinafter referred to as a “rest region”, a “half-pedal region” and a “damper-free region”, respectively. While a player is pressing down the damper pedal, the damper pedal is firstly moved in the rest region, passes through the half-pedal region, and finally enters the damper-free region. 
     While the damper pedal is moving in the rest region the damper mechanism takes up the movement of the damper pedal, and the damper still exerts the force on the string as large as the force at the rest position. When the damper pedal enters the half-pedal region, the damper starts to reduce the force exerted on the string. However, the damper is still in contact with the string. The damper pedal is lightly in contact with the string in the half pedal region, and makes the loudness of tones reduced through the decay of the vibrations of string. When the damper pedal enters the damper-free region, the damper is spaced from the string and any permits the string freely to vibrate. As a result, the tones are prolonged. The players sometimes keep the damper pedal in the half-pedal region and in the damper-free region so as to give delicate artificial expressions to the acoustic piano tone or tones. 
     While a user is performing a music passage in the mute mode, the electronic system is expected correctly to discriminate the half-pedal region from the rest region and damper-free region so as to give the appropriate effect to the electronic tone or tones. In order to monitor the damper pedal, a pedal sensor is provided in association with the damper pedal, and reports the pedal stroke to the controller. The controller determines the pedal region on the basis of the pedal stroke. However, the player feels the effect of damper pedal different between the acoustic piano tones and the electronic tones. The difference in pedal effect also takes place in the recording. 
     The reason why the damper pedal gives the effect to the electronic tones differently from the acoustic piano tones is the relative sensor position to the damper pedal. Although workers of the manufacturer try to locate the pedal sensors at a target position with respect to the damper pedals in the factory, a small amount of deviation is unavoidable. Moreover, the pedal sensors may be slightly moved from the target position after the delivery to users. Thus, the unstable sensor position is a problem of the prior art mute piano. The unstable sensor position is also the trouble in other sorts of keyboard musical instruments such as, for example, an automatic player piano and electronic keyboards. 
     A counter measure is proposed in Japanese Patent Publication No. Hei 8-7575. In the Japanese Patent Publication, the damper pedal stroke is correlated with the amount of mean current of the driving signal. It is important exactly to discriminate the half-pedal region from the other two regions. In order precisely to determine the damper pedal stroke around the boundary between the half pedal region and the other two regions, the prior art inventor proposes in the Japanese Patent Publication that damper pedal stroke is determined at high resolution in the half pedal region and at low resolution in the other regions. The relation between the actual pedal stroke and the modified pedal stroke at different resolution is defined in the normalization table and inverted normalization table. 
     The prior art inventor further proposes to calibrate the relation in the half pedal region. Although the relation between the pedal stroke and the amount of mean current of driving signal is corrected through the modified pedal stroke, the individualities of automatic player piano are not taken into account for the relation between the actual pedal stroke and the amount of means current of driving signal. As a result, the half pedal effect and damper effect are not exactly given to the piano tones in the playback. This is the problem inherent in the prior art controller disclosed in the Japanese Patent Publication. 
     SUMMARY OF THE INVENTION 
     It is therefore an important object of the present invention to provide a keyboard musical instrument, through which different pedal effects are given to tones exactly same as an original performance. 
     It is also an important object of the present invention to provide a controlling system, which is incorporated in the keyboard musical instrument. 
     To accomplish the object, the present invention proposes to optimize relation between an input value and the value of a music data code expressing a pedal effect to be given to the tones. 
     In accordance with one aspect of the present invention, there is provided a musical instrument for producing pieces of music data expressing tones, and the musical instrument comprises a keyboard having plural keys selectively depressed so as to specify pitch of the tones, at least one pedal pressed down so as to specify to a pedal effect to be given to at least one of the tones and moved along a pedal trajectory divided into more than two regions assigned to the tones without any pedal effect and plural pedal effects different from one another, a tone generator connected to the plural keys and the aforesaid at least one pedal, producing the tones at the specified pitch and giving the pedal effect to the aforesaid at least one of the tones, plural key sensors monitoring the plural keys and producing key signals representative of key movements, at least one pedal sensor monitoring the aforesaid at least one pedal and producing a pedal signal representative of a pedal movement on the pedal trajectory and a controller connected to the plural key sensors and the aforesaid at least one pedal sensor, producing music data codes defined in music protocols and expressing at least the specified pitch of the tones and the pedal effect to be given to the aforesaid at least one of the tones on the basis of the key signals, the pedal signal and relation between an input value expressing a current physical quantity of the aforesaid at least one pedal and a value of the music data code expressing the pedal effect and having a memory storing the relation in a rewritable manner so as to make it possible to optimize the relation with respect to actual movements of component parts of the tone generator related to the pedal effects. 
     In accordance with another aspect of the present invention, there is provided a controlling system for a musical instrument having plural keys respectively assigned pitch names of tones to be produced and at least one pedal moved along a pedal trajectory divided into more than two regions assigned to the tones without any pedal effect and plural pedal effects different from one another, and the controlling system comprises plural key sensors monitoring the plural keys and producing key signals representative of key movements, at least one pedal sensor monitoring the aforesaid at least one pedal and producing a pedal signal representative of a pedal movement on the pedal trajectory and a controller connected to the plural key sensors and the aforesaid at least one pedal sensor, producing music data codes defined in music protocols and expressing at least the specified pitch of the tones and the pedal effect to be given to the aforesaid at least one of the tones on the basis of the key signals, the pedal signal and relation between an input value expressing a current physical quantity of the aforesaid at least one pedal and a value of the music data code expressing the pedal effect and having a memory storing the relation in a rewritable manner so as to make it possible to optimize the relation with respect to actual movements of component parts of the tone generator related to the pedal effects. 
    
    
     
       BRIEF DESCRIPTION OF TI-IE DRAWINGS 
       The features and advantages of the keyboard musical instrument and controlling system will be more clearly understood from the following description taken in conjunction with the accompanying drawings, in which 
         FIG. 1  is a cross sectional side view showing the structure of a mute piano according to the present invention, 
         FIG. 2  is a cross sectional side view showing a hammer, a hammer stopper and a damper incorporated in the mute piano, 
         FIG. 3  is a block diagram showing the system configuration of a controller incorporated in the mute piano, 
         FIG. 4  is a graph showing contents of a damper pedal table, and 
         FIGS. 5 and 6  are flowchart showing an essential part of a computer program installed in the mute piano. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description, term “front” is indicative of a relative position closer to a player, who gets ready to play a tune, than a relative position modified with term “rear”. A line drawn between a front position and a corresponding rear position extends in a “fore-and-aft direction”, and a lateral direction crosses the fore-and-aft direction at right angle. An “up-and-down direction” is normal to a plane defined by the fore-and-aft direction and lateral direction. “Clockwise direction” and “counter clockwise direction” are determined on the sheet of paper where a figure, which is just referred to, is drawn. 
     A musical instrument embodying the present invention is used for producing tones expressed by pieces of music data, and comprises a keyboard provided with plural keys, at least one pedal, a tone generator, plural key sensors, at least one pedal sensor and a controller. The keys and pedal are connected to the tone generator and the key sensors and pedal sensor are connected to the controller. 
     The keys are selectively depressed in a performance on a music passage so as to specify pitch of the tones, and the pedal pressed down in the performance so as to specify to a pedal effect to be given to at least one of the tones. The pedal is moved along a pedal trajectory, which is divided into more than two regions, and the more than two regions are assigned to the tones without any pedal effect and plural pedal effects different from one another. Thus, the pedal effect to be given to the tones is depending upon the region where the pedal is found. The tone generator produces the tones at the specified pitch. Certain component parts of tone generator relate to the pedal effects so that the pedal effect is given to at least one of the tones through the behavior of the component parts. 
     The plural key sensors monitor the plural keys, respectively, and the pedal sensor monitors the pedal. The plural key sensors produce key signals representative of key movements, and the key signals are supplied to the controller. Similarly, the pedal sensor produces a pedal signal representative of a pedal movement on the pedal trajectory, and the pedal signal is supplied to the controller. 
     While the plural keys and pedal are being selectively depressed in the performance, the controller produces music data codes defined in music protocols. When the keys are depressed, the controller produces the music data codes expressing at least the specified pitch of the tones on the basis of the key signals. On the other hand, when the pedal is pressed down, the controller produces the music data codes expressing the pedal effect to be given to at least one of the tones on the basis of the pedal signal and relation between an input value expressing a current physical quantity of the pedal and a value of the music data code expressing the pedal effect. 
     In order to store the relation, the controller has a memory, and the memory permits a worker or user to rewrite the relation. In case where the user finds the controller to give a pedal effect different from the effect to be given to the tones, the relation is optimized. In the optimizing work, a worker draws his or her attention to the actual movement of the component parts of the tone generator, and inspects the relation for the mismatch between the more than two regions and the pedal effects. If the mismatch is found, the relation is corrected, and is stored in the memory, again. Thus, the worker makes it possible exactly to give the pedal effects to the tones through the correction of the relation. 
     Referring to  FIG. 1  of the drawings, a mute piano embodying the present invention largely comprises an upright piano  1 , an electronic tone generating system  2  and a mute system  3  and, and the mute system  3  and electronic tone generating system  2  are installed in the upright piano  1 . 
     The upright piano is equipped with a mechanical tone generating system  4  and a pedal system  5 . A player produces acoustic piano tones along music passages through the mechanical tone generating system  4 , and gives effects to the acoustic piano tones through the pedal system  5 . The electronic system  2  monitors the mechanical tone generating system  4  and pedal system  5 . The player produces electronic tones through the electronic tone generating system  2  at the pitch of corresponding acoustic piano tones to be produced, and gives the effects to the electronic tones as similar to those given to the acoustic piano tones. 
     The mute system  3  is provided in association with the mechanical tone generating system  4 , and makes the mechanical tone generating system  4  active and inactive. While the mute system  3  is making the mechanical tone generating system  4  active, the mute piano is in the acoustic playing mode, and a player plays pieces of music on the upright piano  1  through the acoustic piano tones. On the other hand, when mute system  3  makes the mechanical tone generating system  4  inactive, the mute piano is changed to the mute mode so that the acoustic piano tones are not produced. Instead, the player hears the electronic tones produced through the electronic tone generating system  2 . In this instance, the electronic tones are produced on the basis of a set of music data codes supplied from the outside of the mute piano through the electronic tone generating system  2  so that the mute piano has not only the mute mode but also an electronic tone playing mode. 
     The upright piano  2  further includes a keyboard  201 , strings  4 , dampers  205 , action units  210 , a piano cabinet  202 , hammers  215 . The keyboard  201  is placed on a keyboard  202  of the piano cabinet  202 , and the strings  4 , dampers  205 , action units  210  and hammers  215 , which form in combination the mechanical tone generating system  4 , is housed in the piano cabinet  202 . An upper front board  24  of the piano cabinet  202  laterally extends over the keyboard  201 , and a top board  25  defines the uppermost extent of the piano cabinet  202 . 
     The keyboard  201  has black keys  201   a  and white keys  201   b , and pitch names are respectively assigned to the black and white keys  201   a  and  201   b . In this instance, eighty-eight keys  201   a  and  201   b  are incorporated in the keyboard  201 , and are laid on the well-known pattern. A balance rail  203  laterally extends on the key bed  202   a , and offers fulcrums to the black keys  201   a  and white keys  201   b . The black keys  201   a  and white keys  201   b  independently pitch up and down. 
     Capstan screws  211  are upright from the rear portions of the black keys  201   a  and white keys  201   b , and are respectively connected to the action units  210 . For this reason, the movements of the black and white keys  201   a  and  201   b  make the associated action units  210  actuate. The hammers  215  are associated with the action units  210 , respectively, and are driven for rotation toward the strings  204  through escape. 
     The action unit  210  includes a back check  210   a , a damper spoon  210   b , a whippen assembly  212  and a jack  213 . A center rail  202   b  extends in the lateral direction over the rear portions of the black and white keys  201   a  and  201   b , and is supported by action brackets (not shown) on the key bed  202   a . Whippen flanges  210   c  are secured to the center rail  202   b  at intervals, and one of the whippen flanges  210   c  is assigned to the action unit  210 . The whippen assembly  212  is connected to the whippen flange  210   c , and is rotatable about the whippen flange  210   c . The back check  210   a  projects from the front portion of the whippen assembly  212  in the upward direction, and a damper spoon  210   b  projects at the back of the whippen flange  210   c  in the upward direction. The jack  213  is connected to the intermediate portion of the whippen assembly  212  by means of a pin  210   d  so that the jack  213  and whippen assembly  212  are rotatable with one another. The jack  213  and back check  210   a  are provided in association with the hammer  215 , and the damper spoon  210   b  is connected to the damper  205 . The jack  213  and back check  210   a  and the damper spoon  210   b  are hereinlater described in conjunction with the hammer  215  and damper  205 . 
     The strings  204  are designed to produce the acoustic piano tones at the pitch names assigned to the associated black and white keys  201   a  and  201   b , and are provided on trajectories of the associated hammers  215 . The hammers  215  are brought into collision with the strings  204  at the end of rotation, and give rise to vibrations of the associated strings  204 . The acoustic piano tones are produced through the vibrations of the strings  204 . 
       FIG. 2  shows the damper  205 , action unit  210 , hammer  215  and a hammer stopper  30 , which forms a part of the mute system  3 . Damper lever flanges  202   c  and hammer butt flanges  202   d  are secured to the center rail  202   b . The damper lever flanges  202   c  are assigned to the dampers  205 , respectively, and hammer butt flanges  202   d  are respectively assigned to the hammers  215 . One of the damper lever flanges  202   c  and one of the hammer butt flanges  202   d  are respectively provided for the damper  205  and hammer  215 . 
     The damper  205  has a damper head  205   a , a damper lever  205   b  and a damper wire  206 . The damper lever  205   b  is connected to one of the damper lever flanges  202   c  by means of a pin  205   c , and is rotational about the damper lever flange  202   c . The damper wire  206  projects from the upper end surface of the damper lever  205   b  in the upward direction, and the damper head  205   a  is connected to the leading end of the damper wire  206 . The lower end portion of the damper lever  205   b  is held in contact with the damper spoon  210   b  (see  FIG. 1 ). 
     While the associated action unit  210  is being actuated by the depressed key  201   a / 201   b , the action unit  210  causes the damper lever  205   b  to rotate in the counter clockwise direction. The damper spoon  210   b  exerts force on the lower end portion of the damper lever  205   b , and gives rise to rotation of the damper lever  205   b  in the counter clockwise direction. The damper head  205   a  is gradually spaced from the string  204  so as to permit the string  204  to vibrate. 
     The hammer  215  includes a hammer shank  214 , a hammer head  215   a , a hammer butt  215   b  and a catcher  215   c . The hammer butt  215   b  is connected to the hammer but flange  202   d  by means of a pin  215   d  so that the hammer butt  215   b  is rotatable about the pin  215   d . The hammer shank  214  projects from the hammer butt  215   b  in the upward direction, and the catcher  215   c  projects from the hammer butt  215   b  in the frontward direction. The hammer head  215   a  is connected to the leading end of the hammer shank  214 , and is moved on the hammer trajectory which the associated string  204  crosses. 
     While the action unit  210  is staying at the rest position, the jack  213  is held in contact with the lower surface of the hammer butt  215   b , and the back check  210   a  is spaced from the catcher  215   c . The associated black/white key  201   a / 201   b  is assumed to be depressed. The capstan screw  211  (see  FIG. 1 ) pushes the whippen assembly  212  upwardly so that the whippen assembly  212  is rotated in the clockwise direction. The jack  213  pushes the hammer butt  215   b , and gets closer toward an associated regulating button (not shown). When the jack  213  is brought into contact with the regulating button, the jack  213  rotates about the whippen assembly  212  in the counter clockwise direction, and is escaped from the hammer butt  215   b . The jack  213  exerts force on the hammer butt  215   b  during the escape due to the friction, and gives rise to rotation of the hammer  215  in the clockwise direction. Thus, the hammer  215  is driven for rotation by the associated action unit  210 . 
     The hammer head  215   a  is brought into collision with the string  204  at the end of rotation. The hammer  215  rebounds on the string  204 , and starts the rotation in the counter clockwise direction. The catcher  215   c  is bought into contact with the back check  210   a , and stays thereon. 
     When the player releases the depressed key  201   a / 201   b , the rear portion of the black/white key  201   a / 201   b  is sunk due to the weight of the action unit  210 . The whippen assembly  212  is rotated in the clockwise direction together with the jack  213  and back check  210   a . The jack  213  slides into the space below the hammer butt  215   b , and is brought into contact with the lower surface of the hammer butt  215   b , again. The back check  210   a  is left from the catcher  215   c , and, finally, the action unit  210  and hammer  215  return to the rest positions, respectively. 
     A hammer rail  202   e  extends in the lateral direction in front of the hammer shanks  214 , and a hammer rail cloth  202   f  is adhered to the rear surface of the hammer rail  202   e . The hammer shanks  214  rest on the hammer rail  214  at the rest positions. The hammer rail  202   e  is movable in the direction indicated by arrow AR 1 , and pushes the hammer shanks  214  toward the strings  204 . The behavior of hammer rail  202   e  will be described in conjunction with the pedal system  5 . 
     The hammer stopper  30  includes a shaft  31 , brackets  32  cushions  33  and  34  and an electric motor  34  such as a stepping motor. The shaft  31  extends in the space between the hammer shanks  214  and damper wires  206  in the lateral direction, and is rotatably supported by suitable bearings attached to the piano cabinet  202 . The brackets  32  are secured to the shaft  31  at intervals, and are wrapped with the cushions  33 . In this instance, the keyboard  201  is dividable into three registers, and the three brackets  32  are prepared for these three registers. The other cushion  34  is directly adhered to the shaft  31 . The cushions  33  and  34  are made of felt or urethane 
     The electric motor  34  is connected to one end portion of the shaft  31 , and a controller  70  (see  FIG. 1 ) drives the electric motor  34  so as to give rise to the rotation of the shaft  31 . The controller  70  is a system component of the mute system  3 . While the hammer stopper  30  is staying at a free position, the cushions  33  are directed in the upward direction as drawn in real lines in  FIG. 2 , and the hammers  215  are brought into collision with the strings  204  without any interference with the cushions  33 . In other words, the hammer stopper  30  permits the player to produce the acoustic piano tones through the collision between the hammers  215  and the strings  204 . 
     When a player wishes to practice the fingering on the acoustic piano  1  without any acoustic piano tones, the player instructs the controller  70  to direct the hammer stopper  30  to the hammer shanks  214 . Then, the controller  70  energizes the electric motor  34  by means of a current driver  235  (see  FIG. 1 ), and the shaft  31  is rotated in the counter clockwise direction. The current driver  235  is another system component of the mute system  3 . 
     When the cushions  33  are opposed to the hammer shanks  214  as drawn in dots-and-dash lines in  FIG. 2 , the current driver  235  stops the current, and the electric motor  34  does not rotate the shaft  31 . The cushions  33  are moved on the trajectories of the hammers  215 . Thus, the hammer stopper  30  enters the blocking position, and the cushions  33  and other cushion  34  are opposed to the hammer shanks  214  and damper wires  206 , respectively, at the blocking position. 
     The player depresses the black/white key  201   a / 201   b , and the depressed key  201   a / 201   b  actuates the action unit  210 . The damper head  205   a  is spaced from the string  204 , and the damper wire  206  is brought into contact with the cushion  35 . The jack  213  escapes from the hammer butt  215   b , and the hammer  215  starts the rotation toward the string  204 . The hammer  215  starts to travel along the trajectory, and the hammer shank  214  is brought into collision with the cushion  33  before the collision between the hammer head  215   a  and the string  204 . Thus, the hammer stopper  30  makes the hammers  215  rebound thereon before the collision between the hammer head  205   a  and the string  204 . The string  204  does not vibrate, and any acoustic piano tone is not produced. After the rebound on the hammer stopper  30 , the hammers  215  behave as similar to those in acoustic playing mode. Since the jacks  213  escape from the hammer butt  215   b  in the mute mode, the player feels the keytouch usual. 
     Description is hereinafter made on the pedal system  5  with concurrently reference to  FIGS. 1 and 2 . The pedal system  5  includes a damper pedal  240   a , a damper pedal mechanism  241   a , a soft pedal  240   b , a soft pedal mechanism (not shown), a sostenuto pedal  240   c  and a sostenuto pedal mechanism (not shown). 
     The soft pedal mechanism (not shown) is connected to the hammer rail  202   e , and a player decreases the distance between the hammer heads  215   a  and strings  204  by pushing down the soft pedal  240   b . As a result, the hammer heads  215   a  are softly brought into collision with the strings  204 , and the loudness of tones is reduced. The player selectively prolongs the tone by pushing down the sostenuto pedal. A sostenuto rod (not shown) is incorporated in the sostenuto pedal mechanism, and keeps the damper head  215   a  spaced from the string  204  in so far as the player pushes down the sostenuto pedal before releasing the depressed key  201   a / 201   b.    
     A damper rod  241   b  is a component part of the damper pedal mechanism  241   a , and a player bi-directionally rotates the damper rod  241   b  with the damper pedal  240   a . When the player pushes down the damper pedal  240   a , the damper rod  241   b  is rotated in the counter clockwise direction, and the damper rod  241   b  pushes all of the damper levers  205   b . The damper levers  205   b  are rotated in the counter clockwise direction, and the damper heads  205   a  are spaced from the strings  204 . Thus, the damper pedal  240   a  and damper pedal mechanism  241   a  make the damper heads  205   a  concurrently spaced from the strings  204  regardless of the black and white keys  201   a  and  201   b . The damper pedal mechanism  241   a  keeps the damper heads  205   a  spaced from the strings  204  in so far as the player pushes down the damper pedal  240   a . When the player releases the damper pedal  240   a , the damper rod  241   b  leaves from the damper lever  205   b , and the dampers  205  are spaced from and brought into contact with the strings  204  in response to the movements of black and white keys  201   a  and  201   b.    
     The controller  70  is shared between the electronic tone generating system  2  and the mute system  3 , and the electronic tone generating system  2  further includes an array of key sensors  230 , pedal sensors  242 , amplifiers  250 , a volume controller  250   a , loudspeakers  252  in a speaker box  252 , a plug-fit socket  255  and a headphone  256 . The key sensors  230 , pedal sensors  242  and volume controller  250   a  are connected to the controller  70 , and key position signals KS, pedal position signals PS and a volume control signal VS are respectively supplied from the key sensors  230 , pedal sensors  242  and volume controller  250   a  to the controller  70 . The controller  70  is connected to the amplifiers  250 , which in turn is connected to the plug-in socket  255  and loud speakers  251 , and an audio signal AD is supplied to the plug-in socket  255  and loudspeakers  251 . 
     The controller  70  analyzes pieces of key position data on the key position signals KS and pieces of pedal position data on the pedal position signals PS for the movements of black and white keys  201   a / 201   b  and movements of pedals  240   a / 240   b / 240   c , and produces music data codes representative of pieces of music data expressing a performance on the upright piano  1 . The controller  70  produces the audio signal AD representative of the electronic tones to be produced on the basis of the music data codes, and supplies the audio signal AD through the amplifiers  250  to the loud speakers  252  and the plug-in socket  255 . In this instance, the music data codes are produced in accordance with the MIDI (Musical Instrument Digital Interface) protocols. 
     When a user wishes to hear the electronic tones through the headphone  256 , he or she inserts the plug of the headphone  256  into the plug-in socket  255 . Then, the audio signal AD is supplied to the headphone, only, and any electronic tone is not produced through the loud speakers  252 . On the other hand, in case where the headphone  256  is not connected to the plug-in socket  255 , the audio signal AD is supplied to the loud speakers  251 , and the audio signal AD is converted to the electronic tones through the loud speakers  251 . The user changes the loudness of electronic tones by means of the volume controller  250   a.    
     Photo-interrupters are used as the key sensors  230 , and the detectable range of key sensors  230  are wider than the full stroke of the black and white keys  201   a / 201   b . Thus, the current key position between the rest positions and the end positions is converted to the key position signals KS. 
     Photo-reflectors are used as the pedal sensors  242 , and the detectable range of pedal sensors  242  is wider than the full stroke of the pedals  240   a / 240   b / 240   c . For this reason, the current pedal position on the pedal trajectories is reported to the controller  70 . 
     The hammer stopper  30 , current driver  235  and controller  70  form the parts of the mute system  3  as described hereinbefore. A mode switch  220  serves as a man-machine interface, and also forms a part of the mute system. 
     When a user wishes to perform a piece of music through the acoustic piano tones, he or she selects the acoustic playing mode on the mode switch  220 . A mode signal MS is supplied from the mode switch MS to the controller  70 , and the controller requests the current driver  235  to change the hammer stopper  30  to the blocking position through the rotation of the electric motor  34 . On the other hand, if the user wishes to practice the fingering on the keyboard  201  without disturbance of neighborhood, he or she requests the current driver  235  to change the hammer stopper  30  to the free position through the rotation of the electric motor  34 . Thus, the user changes the mute piano between the acoustic playing mode and the mute mode through the mode switch  220 . 
     Turning to  FIG. 3  of the drawings, the system configuration of controller  70  is illustrated. The controller  70  includes an information processor  10 , internal clocks  11 , a tone generator  13 , a signal interface  17 , a shared bus system  18 , a read only memory  21 , which is abbreviated as “ROM”, a random access memory  22 , which is abbreviated as “RAM” and a flash memory  23 . The information processor  10 , internal clocks  11 , read only memory  21 , random access memory  22 , flash memory  23 , tone generator  13  and signal interface  17  are connected to the shared bus system  18  so that the information processor  10  accesses, supplies and transfers various sorts of information to the other system components  11 ,  21 ,  22 ,  23 ,  13  and  17  through the shared bus system  18 . 
     The information processor  10  is an origin of the information processing capability of the controller  70 , and accomplishes given tasks through execution of instruction codes. 
     The instruction codes are stored in the read only memory  21  together with other control parameters and data tables in the non-volatile manner, and form a computer program. The computer program expresses the tasks, and runs on the information processor  10 . The computer program is hereinlater described in detail. One of the data tables is called as a damper pedal table, and the damper pedal table will be hereinlater described in detail. 
     Three music data codes are stored in the read only memory  21 . One of the three music data codes is indicative of continuous buzzes, another of the three music data codes is indicative of buzzes at relatively long intervals, and yet another of the three music data codes is indicative of buzzes at relatively short intervals. 
     The random access memory  22  offers a temporary data storage to the information processor  10 , and serves as flags. For example, the pieces of key position data, pieces of pedal position data and pieces of music data are, by way of example, stored in the temporary data storage in the random access memory  22 . 
     The internal clocks  11  independently measure the lapse of time. One of the internal clocks is assigned to the time period between a note-on/note-off event and the previous note-on/previous note-off event. 
     The flash memory  23  is electrically programmable and erasable, and pieces of data are held in the flash memory  23  in the non-volatile manner. Default values are stored in the flash memory  23 . One of the default values relates to the damper pedal table, and is expressed as “AD 0 ”. 
     The tone generator  13  includes a waveform memory, plural read-out circuits, a key assigner and effectors. The key assigner assigns the note-on events, which the music data codes express, to the read-out circuits, and the read-out circuits make pieces of waveform data read out from the waveform memory. A digital audio signal is produced from the pieces of waveform data. Certain music data codes stand for the effects of the pedals  240   a / 240   b / 240   c , and the digital audio signal is modified through the effectors in the presence of the certain data codes. The music data codes are produced through the fingering on the keyboard  201 , or are supplied from the outside of the mute piano. 
     The tone generator  13  varies the electronic tones depending upon the current pedal position of the damper pedal  240   a . While the damper pedal  240   a  is staying the rest region, any effect is not given to the electronic tones. The effectors give a half-pedal effect to the electronic tones in the half pedal region, and give a damper effect to the electronic tones in the damper-free position. 
     The signal interface  17  includes analog-to-digital converters, digital-to-analog converters, data buffers, amplifiers and driver circuits. The mode switch  220 , key sensors  230 , a control board  26 , the pedal sensors  242 , current driver  235 , a MIDI interface  14  and the amplifiers  250  are connected to the signal interface. Analog signals such as the mode signal MS, key position signals KS and pedal position signals PS are converted to a digital mode signal MSd, digital key position signals KSd and digital pedal position signals PSd, and the digital signals MSd, KSd and PSd are temporarily stored in the data buffers. The information processor  10  periodically accesses the data buffers, and fetches the digital mode signal MSd, digital key position signals KSd and digital pedal position signals PSd from the data buffers. On the other hand, digital signals such as digital audio signal and digital motor control signal are converted to the analog audio signal AD and analog control signals through the digital-to-analog converters, and the analog signals are supplied to other system components through the amplifiers. The music data codes are transferred between the data buffers and the MIDI interface  14  through the driver circuits, and the information processor  10  periodically fetches the music data codes from the data buffers. Another external instrument  15  is connectable to the MIDI interface  14  so that the music data codes are transferred between the controller  70  and external instrument  15  through the MIDI interface  14 . 
     Various switches are provided on the control board  26 . One of the switches is a power switch, and a user activates the controller  70  by turning on the power switch. Another switch is assigned to the instruction to finish a calibration work, which will be hereinafter described in detail. 
     Description is hereinafter made on a calibration of the electronic tone generating system  2  together with the damper pedal table. The damper pedal table is stored in the read only memory  21 , and  FIG. 4  shows contents PL 1  of the damper pedal table. 
     A message [Bn 40 dd] stands for the effect of the damper pedal in the MIDI protocols. [B] [n]. [4], [0] and [d] are hexadecimal numbers. [Bn] and [40] are a status byte expressing the control change and a data byte expressing the control number and are defined in the MIDI protocols. The third byte [dd] is a data byte expressing a value from [00] to [7F]. The value [dd] is hereinafter referred to as a “MIDI value”. The pedal sensor  242 , which monitors the damper pedal  240   a , supplies the analog pedal signal PS to the signal interface  17 , and is converted to the digital pedal signal PSd. “AD 1 ” stands for the value of the digital pedal signal PSd. The difference between the value AD 1  of digital pedal signal PSd and the default value AD 0  is referred to as an “input value of table”. The input value of table is expressed as [0x bb], and [bb] is hexadecimal numbers. In this instance, the manufacturer writes the default value AD 0  of [0x 40] in the flash memory  23  upon completion of assembling work. 
     The contents PL 1  are prepared as follows. First, a mute piano is prepared, and is same model as the mute piano implementing the embodiment. The black and white keys are repeatedly depressed so that the acoustic piano tones are produced through the mechanical tone generator  4 . The damper pedal  240   a  is pressed down, and the pedal stroke is varied. The digital pedal position signal PSd and music data code, which expresses the effect of damper pedal, are monitored, and the input values of table [0x bb], i.e., (AD 1 −AD 0 ) are correlated with the value [dd] of the music data code. Preliminary plots, which express the relation between the input value of table [0x bb] and the music data codes, are obtained, and the acoustic piano tones in the half-pedal state are correlated with the value [dd] of the music data codes. Thereafter, the preliminary plots are modified in Such a manner that the half-pedal effect is given to the acoustic piano tones at [58] of the third byte of the music data code and input value [0x 00]. As a result, the contents PL 1  of damper pedal table are determined as shown in  FIG. 4 . 
     In the damper pedal table, the input value [0x 00], which is equivalent to the decimal number of zero is correlated with the MIDI value [58], which is equivalent to the decimal number “88”. In other words, then the input value of table [0x bb] is zero, the MIDI value [58] is read out from the damper pedal table, and is supplied to the tone generator  13 . 
       FIGS. 5 and 6  show an essential part of the computer program, and a worker calibrates the electronic tone generating system  2  with the assistance of the computer program. Though not shown in  FIGS. 5 and 6 , the computer program periodically branches into a subroutine program for transferring pieces of data from the signal interface  17  to the random access memory  22 . 
     A worker firstly removes the upper front board  24  from the piano cabinet  202 . The worker may further remove the top board  25  from the piano cabinet  202 . Then, the dampers  205  and strings  204  are exposed to the worker. As a result, the worker can visually confirm the movements of the dampers  205 . 
     The worker energizes the controller  70 . Then, the computer program starts to run on the information processor  10 . First, the information processor  10  initializes other system components of the controller  70  as by step S 101 . The information processor  10  writes initial values into registers, which are prepared in the random access memory  22 , and transfers default values, parameters and tables to the random access memory  22 . Thus, the damper pedal table, three music data codes and default value AD 0  are read out from the read only memory  21  and flash memory  23 , and are written into the random access memory  22  in the initialization at step S 101 . 
     Subsequently, the information processor  10  carries out a preliminary work on the system components of the electronic tone generating system  2  and system components of the mute system  3 . For example, the information processor checks the control board  26 , key sensors  230  and pedal sensors  242  to see whether or not any malfunction is found in those system components in the preliminary work at step S 102 . 
     Subsequently, the information processor  10  checks the mode switch  220  to see whether or not a user instructs to calibrate the damper pedal table as by step S 103 . If the worker wishes to play a piece of music on the mute piano, he or she instructs to enter the acoustic playing mode, mute mode or electronic playing mode, and the answer at step S 103  is given negative “No”. With the negative answer “No”, the information processor  10  proceeds to step S 112 . The jobs at steps S 112  to S 119  will be hereinlater described. 
     Assuming now that the worker instructs the calibration work to the information processor  10  through the mode switch  220 , the answer at step S 103  is given affirmative “Yes” and the information processor  10  proceeds to step S 104 , and checks the power switch to see whether or not the worker wishes to finish the calibration work. Since the worker has just instructed the calibration work, the answer at step S 104  is given negative “No”. 
     With the negative answer “No”, the information processor  10  starts periodically to fetch the value AD 1  of damper pedal stroke represented by the digital pedal position signal PSd as by step S 105 . The values AD 1  of damper pedal stroke are periodically transferred to the random access memory  22 , and the previous value AD 1  is replaced with the new value AD 1 . 
     The worker gradually presses down the damper pedal  240   a . When the damper pedal  240   a  starts to leave from the strings  204 , the user further presses down the damper pedal  240   a  by 1 millimeter, the damper pedal  240   a  surely enters the half pedal region between the rest region and the damper-free region. However, the pedal stroke until the half pedal region is not always 1 millimeter. The pedal stroke to be required is fallen within the range of 1±0.5 millimeter. 
     The information processor  10  subtracts the default value AD 0  from the current value AD 1 , and determines the input value [0x bb] through the subtraction. The information processor  10  looks up the damper pedal table, and reads out the MIDI value [dd] corresponding to the input value [0x bb] from the damper pedal table as by step S 106 . 
     The MIDI values equal to less than [57] are corresponding to the continuous buzzes, the MIDI values between [58] and [7E] are corresponding to the buzzes at relatively long intervals, and the MIDI values equal to or greater than [7F] are corresponding to the buzzes at relatively short intervals. The information processor  10  compares the read-out MIDI value [dd] with the above-described three sections, and determines that the buzzes are to be produced as notification sound. The information processor  10  transfers the music data code representative of the notification sound from the random access memory  22  to the electronic tone generator  13  so that the buzzes are radiated from the loudspeaker  251  as by step S 1107 . 
     After the transfer of the music data code indicative of the notification sound at step S 107 , the information processor  10  checks the random access memory  22  to see whether or not the worker depresses a preliminary admissible key as by step S 108 . In this instance, the black key  201   a  assigned the key number 86 serves as the preliminarily admissible key. 
     While the answer at step S 108  is being given negative “No”, the information processor  10  returns to step S 104 , and reiterates the loop consisting of steps S 104  to S 108 . 
     While the information processor  10  is reiterating the loop consisting of steps S 104  to S 108 , the worker changes the pedal stroke, and visually checks the dampers  205  to see whether or not the dampers  205  surely leave from the strings  204  at the change from the continuous buzzes to the buzzes at relatively long intervals. 
     While the worker is finding the dampers  205  to leave from the strings  204  before and after the change of notification sound, the worker depresses the preliminarily admissible key at the time when the dampers  205  start to leave from the strings  204 , and repeatedly changes the relative position between the damper pedal mechanism  241   a  and the pedal sensor  242 . 
     When the information processor  10  acknowledges that the preliminarily admissible key is depressed, the answer at step S 108  is changed to affirmative “Yes”, and the information processor  10  stores the value AD 1  of damper pedal stroke into the random access memory  22  as by step S 109 . 
     While the worker is seeking the optimum relative position between the damper pedal mechanism  241   a  and the damper pedal sensor  242 , the information processor  10  repeatedly rewrites the value AD 1  in the random access memory  22  every time the worker depresses the preliminarily admissible key  201   a.    
     The information processor  10  checks a decision key to see whether or not the worker decides that the boundary between the rest region and the half pedal region is correct as by step S 110 . While the worker wishes to continue the regulation work, the worker does not depress the decision key, and the answer at step S 110  is given negative “No”. Then, the information processor  10  returns to step S 104 , and reiterates the loop consisting of steps S 104  to S 110 . In this instance, the white key  201   b  assigned the key number 88 serves as the decision key. 
     Thus, the black and white keys  201   a  and  201   b  are used as control switches. This feature makes it possible to reduce the number of switches on the control board  26 . 
     When the worker confirms that the dampers  205  start to leave from the strings  204  at the change of the notification sound, the worker pushes the decision key  201   b , and the answer at step S 110  is changed to affirmative “Yes”. 
     Then, the information processor  10  reads out the current value AD 1  from the random access memory  22 , and rewrites the default value in the random access memory  22  and flash memory  23  from AD 0  to AD 1  as by step S 111 . The current value AD 1  serves as the default value AD 0 . 
     Upon completion of the jobs at step S 111 , the information processor  10  returns to step S 102 , and waits for the next instruction. 
     The calibration work is usually carried out before the delivery to users. However, it is possible to carry out the calibration work by a user or a tuning worker at user&#39;s home. 
     After the calibration work, the mute piano is assumed to be delivered to a user. The user energizes the controller  70 . Then, the information processor  10  carries out the initialization at step S 101  and preliminary work at step S 102 . The user is assumed to give the instruction for the mute mode to the controller  70 . 
     The information processor  10  acknowledges the user&#39;s instruction, and the answer at step S 103  is given negative “No”. With the negative answer at step S 103 , the information processor  10  checks the given instruction to see whether or not the mute piano is to be established in the mute mode as by step S 112 . 
     If the user instructs the electronic playing mode or acoustic playing mode, the answer is given negative “No”, and the information processor  10  proceeds to step S 119  for jobs in the mode requested to the user. 
     In this instance, the user has given the instruction for the mute mode so that the answer at step S 112  is given affirmative “Yes”, and the information processor  10  checks the random access memory  22  to see whether or not the user presses down the damper pedal  240   a  as by step S 113 . While the answer is given negative “No”, the information processor  10  proceeds to step S 116 , and checks the random access memory  22  to see whether or not the user depresses or releases any one of the black and white keys  201   a / 201   b  as by step S 116 . 
     If all of the black and white keys  201   a / 201   b  do not change the key positions, the answer at step S 116  is given negative “No”, and the information processor  10  returns to step 
     When the user depresses or releases a black key  201   a  or a white key  201   b  without pressing down the damper pedal  240   a , the information processor  10  proceeds to step S 117 , and transfers the music data code or codes representative of the note-on event or note-off event for the depressed/released key  201   a / 201   b  to the electronic tone generator  13 . 
     Subsequently, the information processor  10  causes the electronic tone generator  13  to produce the digital audio signal without any damper effect. The digital audio signal is converted to the analog audio signal AD, and the electronic tone or tones are produced through the headphone  256 . 
     If, on the other hand, the user presses down the damper pedal  240   a , the answer at step S 13  is changed to affirmative “Yes”. With the positive answer at step S 113 , the information processor  10  reads out the current value AD 1  and default value AD 0  from the random access memory  22 , and subtracts the default value AD 0  from the current value so as to determine the input value [0x bb]. The information processor  10  accesses the damper pedal table with the input value [0x bb], and reads out the MIDI value [dd] from the damper pedal table as by step S 114 . 
     If both of the current value AD 1  and default value AD 0  are [0x 40], the input value is [0x 00] so that the MIDI value of [58] is read out from the damper pedal table. If the current value AD 1  and default value AD 0  are [0x 4A] and [0x 40], respectively, the input value is [0x 0A] so that the MIDI value is [60], which is greater than [58]. If the current value AD 1  and default value AD 0  are [0x 40] and [0x 45], respectively, the input value is [53] which is less than [58]. 
     The information processor  10  compares the MIDI value [dd] with the boundary between the rest region and half pedal region and boundary between the half pedal region and the damper-free region, and determines that the effect to be given to the electronic tones. The information processor  10  produces the music data code representative of the effect to be given to the electronic tone or tones, and transfers the music data code to the electronic tone generator  13  as by step S 115 . 
     Upon completion of the jobs at step S 115 , the information processor  10  proceeds to step S 116 . When the user depresses a black key  201   a  or a white key  201   b , the information processor  10  transfers the music data code representative of the note-on event to the electronic tone generator  13  at step S 117 . Since the music data code representative of the damper effect or half-pedal effect has been already transferred to the electronic tone generator  13 , the damper effect or hall-pedal effect is given to the electronic tone at step S 118 . 
     Thus, the information processor  10  reiterates the loop consisting of steps S 112  to S 118  until the mute piano exits the mute mode. 
     As will be understood from the foregoing description, the relation between the input value [0x bb] and the MIDI value [dd] is directly calibrated with the assistance of the computer program installed in the controller  70 . In the calibration work, a worker visually confirms the damper actions, and makes the input value [0x bb] at the entry into the half-pedal region consistent with the damper actions. In other words, the electronic entry into the half pedal region on the relation is surely made consistent with the mechanical entry into the half pedal region. Thus, the relation, which the damper pedal table expresses, is correctable on the basis of the damper actions, and is made reliable through the calibration. 
     Moreover, the relation between the input value [0x bb] and the MIDI value is directly calibrated so that neither normalization table nor inverted normalization table is required for the mute piano. 
     In the preferred embodiment, the black key and white key serve as the preliminary admissible key and decision key so that any new switch is not required for the calibration work. 
     Although particular embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. 
     The electric motor  34  may be replaced with a supersonic motor. 
     Multi-contact switches may be used as the key sensors. A velocity sensor or an acceleration sensor is available for the keyboard  201 , because it is possible to convert the velocity and acceleration to the current position. 
     The black key assigned the key number 86 and white key assigned the key number 88 do not set any limit to the technical scope of the present invention. Other keys in the keyboard  201  are available for the preliminarily admission and decision. More than one key  201   a / 201   b  may be concurrently depressed to give user&#39;s instructions. Otherwise, switches on the control board  26  may serve as the preliminarily admission key and decision key. 
     The notification sound does not set any limit into the technical scope of the present invention. Three light sources may be prepared for the three regions, i.e., the rest region, half pedal region and damper-free region so that the controller  70  energizes one of the three light sources depending upon the input value [0x bb]. 
     The damper pedal table does not set any limit to the technical scope of the present invention. The relation between the input value [0x bb] and the MIDI value [dd] may be expressed as an equation so as to make the information processor determine the MIDI value on the basis of the input value [0x bb]. 
     The preliminary admissible key may be depressed at the boundary between the half pedal region and the damper-free region. Otherwise, when the dampers  205  start to leave the strings  204 , the user may admit the entry into the half pedal region. In this instance, the user depresses the preliminary admissible key immediately after the movements of dampers  204 . 
     The input value [0x bb] may be corresponding to the MIDI value [dd] at more than one point. The point at which the input value [0x bb] is correlated with the MIDI value [dd] may be calculated on the basis of the boundary between the rest region and the half pedal region and the boundary between the half pedal region and the damper-free region. When the dampers  205  slightly move on the strings  204 , the damper pedal  240   a  reaches the boundary between the rest region and the half pedal region. When the dampers  205  are spaced from the strings  204 , the damper pedal  240   a  reaches the boundary between the half pedal region and the damper-free region. The point at which the input value [0x bb] is correlated with the MIDI value [dd] may be given as an interior division point. 
     The preliminary admissible key and decision key do not set any limit to the technical scope of the present invention. The dampers  205  may be monitored with sensors. In this instance, the controller  205  judges the half-pedal region on the basis of the detecting signal supplied from the sensors. 
     In the preferred embodiment, the damper pedal  240   a  is pressed down by a user in the calibration work. The user may reduce the force on the damper pedal  240   a  so as to permit the damper pedal  240   a  gradually returns toward the rest position. Otherwise, the user may reciprocally moves the damper pedal  240   a  so as to permit the controller  70  to correlate the input value [0x bb] with the MIDI value [dd] as the mean value between the forward movement the and backward movement. 
     The detectable range of a pedal sensor may be narrower than the detectable range of the pedal sensor  240   a . The pedal sensor may simply turn on and off at a pedal position in the half pedal region. 
     The flash memory  23  does not set any limit to the technical scope of the present invention. Any sort of rewritable memory is available for the default value. The default value may be stored in a hard disk. 
     A solenoid-operated pedal actuator may be temporarily installed for the damper pedal  240   a . The controller  70  presses down and releases the damper pedal  240   a  by means of the solenoid-operated pedal actuator. 
     More than two different effects may be given to the tone or tones depending upon the pedal stroke. For example, the half pedal region may be divided into plural sub-regions, and the half-pedal effect is varied depending upon the sub-region where the damper pedal  240   a  presently travels. 
     The damper pedal  240   a  does not set any limit to the technical scope of the present invention. The calibration work may be carried out for any pedal such as, for example, the soft pedal  240   b  in so far as the player presses down the pedal for more than one effect to be given to the tones. 
     The acoustic piano  1  does not set any limit to the technical scope of the present invention. The present invention may appertain to a percussion musical instrument such as, for example, a celesta. The present invention may appertain to an electric piano. 
     The present invention may appertain to another sort of hybrid keyboard musical instruments such as an automatic player piano and a recording system for an acoustic piano. 
     The calibration mode does not set any limit to the technical scope of the present invention. A calibration system may be physically independent of the mute piano. In this instance, the revised version of damper pedal table is loaded from the calibration system to the flash memory  23  of the controller  70 . 
     The MIDI protocols do not set any limit to the technical scope of the present invention. Any music protocols are employable in so far as the pitch of tones to be produced and pedal effects are defined in the music protocols. 
     The component parts of mute piano are correlated with claim languages as follows. The black keys  201   a  and white keys  201   b  are corresponding to “plural keys”, and the damper pedal  240   a  serves as “at least one pedal”. The rest region, half pedal region and damper-free region are corresponding to “more than two regions”. The mechanical tone generator  4  or the action units  210 , hammers  215 , dampers  205  and strings  204  form in combination a “tone generator”. 
     The key position signals KS and pedal position signal PS are corresponding to “key signals” and a “pedal signal”, respectively. The dampers  205  serve as “component parts”. The flash memory  23 , random access memory  22  and read only memory  21  as a whole constitute a “memory”. The MIDI protocols serve as “music protocols”. The input value [0x bb] expresses the current pedal position on the damper pedal trajectory so that the pedal position is equivalent to a “current physical quantity”. The MIDI protocols are equivalent to “music protocols”. 
     The strings  204  serve as “other component parts” of the tone generator. The amplifiers  250 , loud speakers  251  and headphone  256  as a whole constitute a “sound system”.