Abstract:
A keyboard musical instrument that is equipped with an electric tutor for guiding a trainee in practicing manipulation of black and white piano keys, whereby the electric tutor reads pieces of musical data information representative of the black and white keys to be depressed and a timing to depress each of the black or white keys for guiding the trainee in the fingering. More specifically, while the trainee is practicing a piece of music, the electric tutor automatically sinks the designated black or white keys as an advanced notice to the trainee so that the trainee can prepare to depress the keys at the appropriate timing, and whereby the electric tutor sinks the same keys again for an inductive action at the time when such keys are to be appropriately depressed.

Description:
FIELD OF THE INVENTION 
     This invention relates to a musical education instrument and, more particularly, to an electric tutor, a musical instrument with built-in electric tutor, a method for guiding the fingering on a musical instrument and an information storage medium for storing a computer program representative of the method. 
     DESCRIPTION OF THE RELATED ART 
     It is said that beginners hardly make progress in musical instruments by themselves. The beginner must learn how to read a musical score and practice the fingering in accordance with a series of notes on the musical score. In order to assist the beginner in the practice, electric tutors have been developed for a musical instrument such as, for example, a keyboard musical instrument. A typical example of the electric tutor for a keyboard musical instrument has optical indicators such as an array of light emitting diodes located in proximity to the black/white keys, respectively, and sequentially illuminates the optical indicators. The trainee fingers on the keyboard under the guidance of the electric tutor. Thus, the electric tutor offers the guidance by optically indicating the black/white keys to be depressed. 
     Following problems are encountered in the prior art electric tutors. Although the optical indicators are provided in proximity to the black/white keys, the trainee needs to repeatedly search the array of optical indicators to see what key is to be depressed during the practice. The trainee concentrates the attention to the array of optical indicators. This means that the trainee tends to divert the attention from the fingers on the keyboard. The practice without the attention to the fingers on the keyboard is not desirable. Thus, the prior art electric tutors are less desirable. 
     When the trainee finds the light radiated from an optical indicator during the search, he or she starts to depress the black/white key indicated by the optical indicator. A time lug is unavoidably introduced between the notice of the optical indication and the fingering. Thus, the prior art electric tutor teaches the trainee what keys are to be depressed, but can not exactly teach the timing to depress the keys. 
     SUMMARY OF THE INVENTION 
     It is therefore an important object of the present invention to provide an electric tutor, which directly indicates manipulators to be activated. 
     It is also an important object of the present invention to provide a musical instrument, a built-in electric tutor of which directly indicates manipulators to be activated. 
     It is another important object of the present invention to provide a method used in the electric tutor. 
     It is yet another important object of the present invention to provide an information storage medium, which stores a program representative of the method. 
     To accomplish the object, the present invention proposes to give a previous notice and an inductive action to a black/white key to be depressed. 
     In accordance with one aspect of the present invention, there is provided an electric tutor associated with a musical instrument having plural manipulators for guiding a trainee in a practice on the plural manipulators, and the electric tutor comprises a memory for storing pieces of music data information representative of a performance, a data processor selectively fetching the pieces of music data information and generating a piece of control data information representative of one of the plural manipulators to be manipulated in the practice and another piece of control data information representative of a timing to manipulate the aforesaid one of the plural manipulators and a driver including plural driving units respectively associated with the plural manipulators and responsive to the piece of control data information and the aforesaid another piece of control data information so as to manipulate the aforesaid one of the plural manipulators at the timing to the extent not to generate a sound. 
     In accordance with another aspect of the present invention, there is provided a musical instrument comprising plural manipulators used for specifying an attribute of tones, a tone generating means responsive to the plural manipulators for generating the tones and an electric tutor including a memory for storing pieces of music data information representative of a performance, a data processor selectively fetching the pieces of music data information and generating a piece of control data information representative of one of the plural manipulators to be manipulated in the practice and another piece of control data information representative of a timing to manipulate the one of aforesaid plural manipulators and a driver including plural driving units respectively associated with the plural manipulators and responsive to the piece of control data information and the aforesaid another piece of control data information so as to manipulate the aforesaid one of the plural manipulators at the timing to the extent not to generate the tone. 
     In accordance with yet another aspect of the present invention, there is provided a method for guiding a trainee in a practice on plural manipulator incorporated in a musical instrument comprising the steps of a) determining one of the plural manipulators to be manipulated and a timing to manipulate the aforesaid one of the plural manipulators, b) waiting for the timing and c) manipulating the aforesaid one of the plural manipulators at the timing to the extent not to generate a tone. 
     In accordance with still another aspect of the present invention, there is provided an information storage medium for storing a program representative of a method for guiding a trainee in a practice on plural manipulator incorporated in a musical instrument, and the method comprises the steps of a) determining one of the plural manipulators to be manipulated and a timing to manipulate the aforesaid one of the plural manipulators, b) waiting for the timing and c) manipulating the aforesaid one of the plural manipulators at the timing to the extent not to generate a tone. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the electric tutor, the method and the information storage medium will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a partially cut-away front view showing the structure of an electronic piano equipped with an electric tutor according to the present invention; 
     FIG. 2 is a partially cut-away side view showing the electronic piano; 
     FIG. 3 is a schematic view showing the arrangement of mechanical/electric components of the electronic piano; 
     FIG. 4 is a front view showing the arrangement on a front board of a control unit incorporated in the electronic piano; 
     FIG. 5 is a block diagram showing the arrangement of an electronic data processing system of the control unit; 
     FIG. 6 is a block diagram showing signal flows in the electronic piano; 
     FIG. 7 is a perspective view showing a part of a keyboard incorporated in the electronic piano; 
     FIG. 8 is a view showing MIDI data codes stored in a random access memory device in a control unit; 
     FIG. 9 is a flowchart showing a main routine program; 
     FIG. 10 is a flowchart showing a subroutine program for generating electronic sounds; 
     FIG. 11 is a flowchart showing a subroutine program for a request to guide a trainee in a practice on the acoustic piano; 
     FIG. 12 is a flowchart showing a subroutine program for a timer interruption; 
     FIG. 13 is a flowchart showing a subroutine program for a previous notice; 
     FIG. 14 is a flowchart showing a subroutine program for an inductive action; 
     FIG. 15 is a timing chart showing the guide in the practice on the acoustic piano; 
     FIG. 16 is a flowchart showing another subroutine program for a timer interruption; 
     FIG. 17 is a timing chart showing another guide in the practice on the acoustic piano; and 
     FIG. 18 is a flowchart showing a subroutine program for an indication of direction. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     An electric tutor implementing the first embodiment assists a trainee in a practice of the fingering on a keyboard and steps on a damper pedal both incorporated in an acoustic upright piano. The electric tutor slightly sinks the keys to be depressed in order to guide the trainee in the fingering. The key motion is a previous notice, and teaches the trainee a key to be depressed and the timing to depress the key. The damper pedal is also moved for the previous notice and the timing. 
     Referring to FIGS. 1 and 2 of the drawings, an electronic piano comprises an electric tutor  100  and a keyboard musical instrument  200 . The keyboard musical instrument  200  includes an acoustic upright piano, a silent system  300  and electronic tone generating system, and a keyboard and pedal mechanisms are essential parts of the acoustic upright piano serving as a kind of interface between a pianist and the keyboard musical instrument. In this instance, black/white keys  201  of the keyboard and a damper pedal  202  of one of the pedal mechanisms serve as manipulators. The electric tutor  100  shares a control unit  100 A with the electronic tone generating system. The control unit  100 A guides a trainee in a fingering on the keyboard and steps on the damper pedal, and controls the tone generation in response to the fingering and the steps. 
     Other electric/electronic components are also shared between the electric tutor and the electronic tone generating system. Such shared components are an electric power unit  210  and an interface unit  220 . The electric power unit  210  distributes power voltages to the control unit  100 A and other electric/electronic components. The electric power unit  210  generates a low dc voltage appropriate for a computer system and a high power voltage. The electric power unit  210  supplies the low dc voltage to the control unit  100 A, and the high power voltage through the interface unit  220 . 
     The interface  220  is provided between the control unit  100 A and the other electric/electronic components such as an array of key driver units  230 , an array of key sensors  240 , an array of hammer sensors  250 , a pedal driver unit  260  and pedal sensors  270 . The array of key driver units  230  and the pedal driver units  260  are incorporated in the electric tutor, and the array of key sensors  240 , the array of hammer sensors  250  and the pedal sensors  250  form parts of the electronic sound generating system. They are hereinlater detailed in conjunction with the electric tutor and the electronic sound generating system. 
     The interface  220  includes a controller  221  and power transistors  222 / 223  (see FIG.  3 ). Although a single transistor symbol is labeled with reference numeral  222 , the eighty-eight power transistors  222  are incorporated in the interface  222 , and are independently controlled by the controller  221 . The controller  221  is integrated on a single semiconductor chip, and is connected to the control unit  100 A. The power transistors  222  are respectively connected to the key driver units  230 , and the power transistor  223  is connected to the pedal driver unit  260 . The controller  221  selectively energizes the power transistors  222 / 223  so that the key driver units  230  and the pedal driver unit  260  actuates the black/white keys  201  and the damper pedal  202  under the control of the control unit  100 A. 
     Acoustic Upright Piano 
     The acoustic upright piano is same as a standard upright piano, As shown in FIG. 3, the acoustic upright piano includes the keyboard, key action mechanisms  205  respectively linked with the black/white keys  201  of the keyboard, hammers  253  driven for rotation by the key action mechanisms, respectively, sets of strings  290  to be struck with the hammers  253 , respectively, damper mechanisms  292  actuated by the black/white keys  201  for controlling the vibrations of the strings  290  and the pedal mechanisms  294 . Eighty-eight black/white keys  201  form the keyboard, and are laid on the pattern of the keyboard of the standard upright piano. When a pianist depresses a black/white key  201 , the associated key action mechanism  205  is activated, and causes the associated damper  292  to be spaced from the associated set of strings  290 . The associated key action mechanism  205  drives the associated hammer  253  for rotation through an escape of a jack from the hammer  253 , and the hammer  253  starts a free rotation at the escape. The hammer  253  strikes the associated set of strings  290 , and causes it to vibrate for generating a tone. When the pianist releases the black/white key  201 , the damper  292  is brought into contact with the set of strings  290 , and damps the set of strings  290  down. If the pianist steps on the damper pedal  202 , the pedal mechanism  294  keeps the damper  292  spaced from the associated set of strings  290 , and prolongs the tone. Thus, the acoustic upright piano behaves as similar to the standard upright piano, and no further description is hereinbelow incorporated for the sake of simplicity. 
     Silent System 
     The silent system  300  includes a hammer stopper  301  and a link mechanism connected to the hammer stopper  301 . The hammer stopper  301  is rotatably supported by action brackets (not shown) between the hammer shanks of the hammers  253  and the sets of strings  290 . The pianist manipulates the link mechanism so as to change the hammer stopper  301  between a free position and a blocking position. The hammer stopper  301  at the blocking position is on the trajectories of the hammers  253 , and the hammers  253  rebound on the hammer stopper  301  before striking the sets of strings  290 . On the other hand, when the hammer stopper  301  is changed to the free position, the hammer stopper  301  is positioned out of the trajectories, and the hammers  253  strike the associated sets of strings  290  without any interference of the hammer stopper  301 . 
     Control Unit 
     Turning to FIG. 4 of the drawings, the control unit  100 A has a front board, and a floppy disk drive  110 , a signal output port  120 , a display unit  130  and a manipulating switch panel  140  are arranged on the front board. The floppy disk driver  110  has a slot. A floppy disk is inserted into the slot, and taken out therefrom. Though not shown in the drawings, the floppy disk driver has a magnetic head, and music data codes are written into and read out from the floppy disk through the magnetic head. 
     A speaker system SP and a headphone HH (see FIG. 5) arc connectable to the signal output port  120 , and an audio signal is supplied through the Signal output port  120  to the speaker system SP and/or the headphone HH. Electronic sounds are produced through the speaker system SP and/or the headphone HH. 
     The display unit  130  is implemented by seven-segment light emitting diode arrays or a liquid crystal display. Characters and/or symbols are produced on the display unit  130 , and the player is informed of the state of the electronic piano through the display unit  130 . 
     The manipulating switch panel  140  has an array of manipulating switches. One  141  of the switches is used for a request for an electric guidance, and another switch  142  is used for cancellation of the request. 
     An electronic data processing system is incorporated in the control unit  100 A, and FIG. 5 illustrates the arrangement of the electronic data processing system. The electronic data processing system includes a central processing unit  101 , a read only memory  102 , a random access memory  103 , a signal input/output unit  104 , the floppy disk driver  110 , an electronic tone generator  105 , the display unit  130  and the manipulating switch panel  140 . The central processing unit  101 , the read only memory  102  and the random access memory  103  are abbreviated as “CPU”, “ROM” and “RAM”, respectively. 
     The read only memory  102  serves as a program memory, and various computer programs are stored in the read only memory  102 . The central processing unit  101  sequentially fetches instruction codes of a selected computer program, and executes them. In other words, the computer programs selectively run on the central processing unit  101 . Several computer programs will be hereinlater described in detail. 
     The random access memory  103  serves as a working memory, flags and registers. The music data codes are transferred from the floppy disk to the random access memory  103 , and arc processed by the central processing unit  101 . 
     The signal input/output unit  104  is connected to the controller  221  of the interface unit  220 , and detecting signals and driving signals are transferred from and to the interface unit  220 . The audio signal is supplied from the electronic tone generator  105  through the signal output port  120  to the speaker system SP and/or the headphone HH. 
     Electronic Tone Generating System 
     The control unit  100 A, the array of key sensors  240 , the array of hammer sensors  250  and the pedal sensors  270  are incorporated in the electronic tone generating system. The key sensors  240  are respectively provided under the black/white keys  201 , and monitor the associated black/white keys  201 . If a black/white key  201  is depressed and, thereafter, released, the black/white key is moved toward the end position, and returns toward the rest position. The associated key sensor  240  detects the key motion, and varies a key position signal representative of a current position of the black/white key  201 . In this instance, the key sensor  240  is the combination of a shutter plate  241 , a light emitting element  242  and an optical fiber  243 , and a photoelectric converter unit  281  is shared between the key sensors  240  and the hammer sensors  250 . The shutter plate  241  is attached to the lower surface of the black/white key  201 , and the light emitting element  242  is opposed to an incident end of the optical fiber  243  across the trajectory of the associated black/white key  201 . 
     The hammer sensors  250  are respectively provided for the hammers  253 , and monitor the associated hammers  253 . When a black/white key  201  is depressed, the associated key action mechanism  205  drives the hammer  253  for rotation, and the hammer  253  strikes the set of strings  290 . The associated hammer sensor  250  detects the impact against the set of strings  290 , and produces a hammer detecting signal representative of the impact with the hammer  253 . In this instance, the hammer sensor  250  is the combination of a shutter plate  251 , a light emitting element  252  and an optical fiber  253 . The shutter plate  251  is attached to the hammer shank of the hammer  253 , and the light emitting element  252  is opposed to an incident end of the optical fiber  253  across the trajectory of the associated hammer  253 . 
     The optical fibers  243  and  253  are connected to the photo-electric converting unit  281 , and the photo-electric converter unit  281  produces the key position signals and hammer detecting signals. The photo-electric converting unit  281  supplies the key position signals and the hammer detecting signals to a sensor board  282 . The sensor board  282  will be described hereinbelow. 
     The optical sensor disclosed in Japanese Patent Publication of Unexamined Application No. 9-54584 is available for the key sensors  240  and the hammer sensors  250 . The optical sensor disclosed in the Japanese Patent Publication of Unexamined Application has a sensor box, and a slit is open to the shutter plate like the shatter plates  241 / 251 . When the key/hammer is rotated, the shutter plate projects through the slit into the inner space of the sensor box. A light emitting sensor head is opposed to a light receiving sensor head across the trajectory of the shutter in the inner space. A light emitting diode is connected through an optical fiber to the light emitting sensor head, and the light receiving sensor head is connected through an optical fiber to a photo-detecting diode of the photo-electric converting unit. A light beam bridges the space between the light emitting sensor head and the light receiving sensor head. The light beam is of the order of 5 millimeters in diameter. The shutter plate gradually intercepts the light beam, and, accordingly, the amount of light on the light receiving sensor head is reduced. The photo-detecting diode generates photo-current proportional to the amount of light received, and the photo-electric converting unit produces an analog Signal varied with the current position of the shutter plate and, accordingly, the black/white key or the hammer. 
     Electric switches  271  serve as the pedal sensors  270 , respectively. The electric switches  271  are respectively associated with the three pedal mechanisms  294 . When the player steps on the pedals, the pedals pull down the associated pedal mechanisms  294 , and the pedal mechanisms  294  close the associated electric switches  271 . The electric switches  271  produce pedal detecting signals, and supply the pedal detecting signals to the sensor board  282 . 
     The controller  100 A receives digital data codes Sh representative of a performance on the acoustic upright piano from the sensor board  282 . The controller  100 A records the music data codes in a floppy disk, and/or transfers them to the outside thereof. The controller  100 A further produces the audio signal from the music data codes, and supplies the audio signal to the speaker system SP and/or the headphone HH. In FIG. 3, the signal flow for the electronic tone generating system is indicated by white arrows. 
     Electric Tutor 
     The electric tutor includes the controller  100 A, the array of the key drive units  230  and the pedal drive unit  260 . Electromagnetic actuators  231  serve as the key drive units  230 , respectively, and are provided under the rear end portions of the black/white keys  201 , respectively. The electromagnetic actuator  231  has a solenoid unit and a plunger. The solenoid units of the electromagnetic actuators  231  are respectively connected in parallel between the electric power source  210  and the power transistors  222 , and the high power voltage is supplied from the electric power source  210  through the interface  220  to the solenoid units. When the controller  221  makes a power transistor  222  turn on, the electric current flows through the solenoid unit of the associated electromagnetic actuator  231 , and the solenoid unit creates magnetic field in around the solenoid unit. Then, the plunger upwardly projects from the solenoid unit, and pushes the rear end portion of the associated black/white key  201 . The stroke of the plunger is short, and the electromagnetic actuator causes the front end portion of the associated black/white key  201  to slightly sink. The stroke is so short that the jacks of the key action mechanisms  205  do not escape from the associated hammers  253 . 
     The pedal drive unit  260  is also implemented by an electromagnetic actuator  261 . The electromagnetic actuator  261  has a solenoid unit and a plunger. The plunger forms a part of the pedal mechanism  294  for the damper pedal  201 , and passes through the associated solenoid unit. The solenoid unit is connected between the electric power source  210  and the power transistor  223 . When the controller  221  causes the power transistor  223  to turn on, the high power voltage is applied to the solenoid unit, and the electric current flows through the solenoid unit and the power transistor  223  to a discharge line. The solenoid unit creates the magnetic field, and the plunger is upwardly moved. The stroke is so short that the damper pedal is a little depressed. The damper pedal  202  does not space the damper mechanisms  292  from the associated sets of strings  290 . 
     While a trainee is practicing on the acoustic upright piano  200 , the control unit  100 A instructs the controller  221  to selectively energize the solenoid units of the electromagnetic actuators  242 / 261 . The electromagnetic actuators  242 / 261  slightly sink the black/white keys  201  and the damper pedal  202 , and guide the trainee through previous notices and inductive actions. The previous notices are given to the fingers prior to timings to manipulate the black/white keys  201  and the damper pedal  202 , and the inductive actions are given to the fingers and the foot at the timings to manipulate the black/white keys  201  and the damper pedal  202 . The previous notices and the inductive actions are directly given to the fingers and the foot, and the trainee pays the attention to the fingers and the foot. The trainee can concentrate the eyes on the music score, and learns the piece of music through the music score and the guidance corresponding to the passage of the piece of music. In FIG. 3, the signal propagation and the motions of the component members are indicated by black arrows. 
     Thus, the electric tutor according to the present invention twice sinks a black/white key  201  to be depressed and the damper pedal  202 . The black/white key  201  is a little sunk from the rest position before the timing to depress it for the previous notice, and returns to the rest position. When the timing comes, the black/white key  201  is sunk for the inductive action at the timing. Then, the trainee depresses the black/white key  201 . The damper pedal  202  is also twice sunk for the previous notice and the inductive action. Thus, the electric tutor twice sinks the manipulators, i.e., the black/white keys  201  and the damper pedal  202  so as to guide a trainee in the practice on the piano. 
     Operations 
     Description is hereinbelow made on operations of the electronic piano. FIG. 6 illustrates signal flows in the operation. Real lines are indicative of the signal flow for the electric tutor, and broken lines are indicative of the signal flow for the electronic tone generating system. 
     The electronic tone generating system behaves as follows. A player changes the hammer stopper  301  to the blocking position, and instructs the control unit  100 A to produce electronic sounds. The key sensors  240 , the hammer sensors  250  and the pedal sensors  270  start to respectively monitor the associated black/white keys  201 , the hammers  253  and the pedal mechanisms  294 . 
     The player is assumed to depress a black/white key  201 . The shutter plate  241  gradually reduces the amount of light transferred through the optical fiber  243  to the photo-electric converting unit  281 , and the photo-electric converting unit  281  decreases the magnitude of the key position signal representative of the current key position of the black/white key  201 . The depressed black/white key  201  actuates the associated key action mechanism  205 , and the key action mechanism  205  drives the associated hammer  253  for the free rotation. The sensor board  282  processes the key position signal, and determines a key velocity. The sensor board  282  produces pieces of music data information representative of a note number assigned to the depressed black/white key  201  and the key velocity. 
     The hammer  253  continues the free rotation toward the set of strings  290 , and the hammer sensor  250  decreases the amount of light. Accordingly, the photo-electric converting unit  281  decreases the magnitude of the hammer detecting signal, and supplies the hammer detecting signal to the sensor board  282 . The hammer  253  rebounds on the hammer stopper  301  immediately before the strike at the set of strings  290 , and the sensor board  282  determines the time to be an impact timing. The sensor board  282  produces a piece of music data information representative of a key-on event. 
     The black/white key  201  returns toward the rest position, and the key sensor  240  increases the amount of light. The photo-electric converting unit  281  increases the magnitude of the key position signal, and supplies the key position signal to the sensor board  282 . The sensor board  282  determines a timing at which the damper  292  is brought into contact with the set of strings  290 . The sensor board  282  produces a piece of music data information representative of the timing. 
     If the player steps on the damper pedal  202 , the pedal sensor  270  detects the motion of the damper pedal  202 , and supplies the pedal detecting signal to the sensor board  282 . The sensor board  282  produces a piece of music data information representative of the prolongation of the electronic tone. 
     When the player instructs the control unit  100 A to generate electronic sounds, the sensor board  282  starts to increment a counter (not shown) for a piece of control data information representative of a lapse of time or a duration time. The sensor board  282  produces digital data codes Sh such as, for example, MIDI (Musical Instrument Digital Interface) codes from the pieces of music data information and the piece of control data information. The digital data codes Sh are transferred from the sensor board  282  to the control unit  100 A. The control unit  100 A may transfer the digital data codes Sh to the floppy disk driver  110  and/or an external system (not shown) through a communication line. The floppy disk driver  110  stores the digital data codes Sh in a suitable information storage medium such as a floppy disk. The control unit  100 A further transfer the digital data codes to the electronic tone generator  105 , and the electronic tone generator  105  generates the audio signal from the digital data codes. The audio signal is supplied through the signal output port  120  to the speaker system SP and/or the headphone HH, and the speaker system SP and/or the headphone HH generates the electronic tones corresponding to the acoustic tones not produced. 
     FIG. 7 shows a stroke Lh of the white key  201  depressed by a player in a performance and a stroke Ls of the white key  201  sunk by the key driver unit  230  for the previous notice or the inductive action. The strokes Lh/Ls are measured from the rest positions, and the stroke Lh is longer than the stroke Ls. When the key driver unit  230  moves the associated black/white key  201 , the key position signal is decreased to a value corresponding to the stroke Ls. However, the key position signal does not exceed the value. The sensor board  282  checks the key position signal to see whether or not the stroke exceeds Ls. If the stroke does not exceed Ls, the sensor board  282  ignores the key motion, and does not supply the digital data code Sh through the interface unit  220  to the control unit  100 A. On the other hand, if the stroke exceeds Ls, the sensor board  282  continues to monitor the key position signal and the hammer detecting signal, and supplies the digital data codes Sh through the interface unit  220  to the control unit  100 A. There is a play between a black/white key of an acoustic piano and a key action mechanism, and the play takes up the key motion before the depressed key actuates the key action mechanism. The manufacturer may adjust the short stroke Ls to the stroke corresponding to the play. 
     The electric tutor behaves as follows. A standard performance is given in the form of a set of digital data codes, which is usually stored in a floppy disk. A trainee is assumed to request the electric tutor to guide him in the practice on the acoustic piano  220  by manipulating the switch  141 . The electric tutor transfers the set of digital data code from the floppy disk to the random access memory  103 . 
     FIG. 8 shows a part of the set of digital data codes stored in the random access memory  103 . The digital data codes are formed in accordance with the MIDI standards. Most of the MIDI codes are broken down into two categories, i.e., the duration data and the event data. The event data represents one of the note-on and the note-off, the note number assigned to a depressed black/white key  201  and a velocity. The velocity is corresponding to the strength of force exerted on the depressed black/white key  201  and, accordingly, the strength of the impact. 
     The MIDI data codes are sequentially stored in the random access memory. The duration data code is representative of a relative time period between two events or the duration time. In this instance, a number of clock pulses is used as the duration time. The MIDI standards define that a quarter note is corresponding to twenty-four clock pulses of the MIDI timing clock signal. The time period for each quarter note is variable with a tempo so that the controller  100 A determines the absolute time period between the events on the basis of the duration time and the tempo. If the tempo is 60, a minute is corresponding to sixty quarter notes, and each quarter note defines a second. Then, each MIDI timing clock is corresponding to a twenty-fourth second. The duration data stored in address “1” indicates that the duration time is 100 (see the first row of FIG.  8 ). The absolute time to the next event is approximately equal to 4 seconds, i.e., 100×({fraction (1/24)})≈4. The control data representative of the tempo may be given by using a switch on the manipulating board  140 . Otherwise, the control data representative of the tempo may be stored in the floppy disk. The control data may be stored at address “1”, and the duration/event data codes may be stored from address “2” to address “n+1”. In this instance, the previous notice is given to the trainee earlier than the inductive action by fifty clock pulses of the MIDI timing clock signal. Each event data code represents the kind of event, i.e., the note-on or the note-off, the note number and the velocity as shown in FIG.  8 . The note number represents the pitch of a tone or a pitch name. The note number “60” is assigned to the pitch name “C” in the center scale on the keyboard of the acoustic piano  200 . The note number is incremented from 0 to 127 at intervals of semitone. For this reason, when a note number is given to the control unit  100 A, the control unit  100 A selects a black/white key  201  to be depressed from the keyboard. 
     Thus, a set of digital data codes representative of a standard performance is stored in the random access memory  103 , and a computer program runs on the central processing unit  101  so as to guide the trainee in the practice on the acoustic piano  200  as will be hereinlater described in detail. 
     Computer Programs 
     Computer programs for the electronic tone generating system and the electric tutor are stored in the read only memory  102 , and the computer programs selectively run on the central processing unit  101  as follows. 
     FIG. 9 shows a main routine program. When the control unit  100 A is powered, the central processing unit  101  starts to sequentially execute programmed instructions of the main routine program. The central processing unit  101  firstly initializes the other units as by step S 10 . The registers and the flags in the random access memory  103  are cleared and/or default values are stored therein. 
     One of the flag BF is assigned to the request to the electric tutor. When the start switch  141  is manipulated, the flag BF is changed to “1” representative of the request for the guide. On the other hand, when the stop switch  142  is manipulated, the flag BF is changed to “0” representative of the cancellation of the request for the guide. Four registers D 1 , D 2 , AD 1  and AD 2  are used for the electric tutor (see FIG.  15 ). A time period until the next previous notice is stored in the register D 1 , and a time period until the next inductive action is stored in the register D 2 . The duration data are used for the time periods. The address stored in the register AD 1  is indicative of the memory location where the MIDI to be read out for the previous notice is stored. On the other hand, the address stored in the register AD 2  is indicative of the memory location where the MIDI data code to be read out for the inductive action is stored. 
     Upon completion of the initialization, the central processing unit  101  proceeds to step S 20 , and is branched to a sub-routine for generating electronic tones. If the acoustic tones are selected, the central processing unit  101  skips step S 20 , and immediately returns to the main routine program. When the electronic tones are selected, the electronic tone generating system is activated, and electronic tones are generated on the basis of the pieces of music data information Sh. A sub-routine program for generating electronic tones is shown in FIG. 10, and is detailed hereinlater. 
     When the central processing unit  101  returns from the sub-routine program for generating electronic tones to the main routine program, the central processing unit  101  proceeds to step S 30 , and is branched to a sub-routine for the guide. Sub-routine programs for the guide are shown in FIGS. 11,  12 ,  13  and  14 , and will be hereinlater described in detail. 
     Upon completion of the subroutine program or programs for the guide, the central processing unit  101  proceeds to step S 40 , and searches the manipulating switch panel  140  for a newly depressed switch. If a switch is newly depressed, the central processing unit  101  interprets the instruction given through the depressed switch, and changes the contents of the flag/register. If there is not any depressed switch or the above-described job is completed, the central processing unit  101  proceeds to step S 50 , and carries out other jobs. When the other jobs are completed, the central processing unit  101  returns to step S 20 . Thus, the central processing unit  101  reiterates the loop consisting of steps S 20 , S 30 , S 40  and S 50  until the electric power is removed from the control unit  100 A. 
     The subroutine program for generating electronic tones is hereinbelow detailed with reference to FIG.  10 . The central processing unit  101  firstly checks the signal input/output unit  104  to see whether or not the player depresses or releases any one of the black/white keys  201  or any one of the pedals as by step S 21 . If the answer at step S 21  is given negative, the central processing unit  101  immediately returns to the main routine program. On the other hand, if the answer at step S 21  is given affirmative, the central processing unit  101  produces a music data code from the pieces of music data information Sh related to the manipulated key  201  or the manipulated pedal as described in conjunction with the electronic tone generating system. The central processing unit  201  supplies the audio signal through the signal output port  120  to the speaker system SP and/or the headphone, and the electronic tone is generated as by step S 22 . Thereafter, the central processing unit  201  returns to the main routine program. 
     In the following description, a trainee is assumed to practice a piece of music represented by the MIDI data codes shown in FIG. 8, and the electric tutor guides the trainee in the practice on the acoustic piano as shown in FIG.  15 . When the central processing unit  201  is branched to the subroutine for guiding the tutor in the practice on the acoustic piano, the central processing unit  201  checks the manipulating switch board.  140  to see whether or not the start switch  141  is manipulated as by step S 31  (see FIG.  11 ). If the start switch  141  has been manipulated, the answer at step S 31  is given affirmative, and the central processing unit  141  changes the flag BF to “1” as by step S 32 . The central processing unit  201  instructs the floppy disk driver  110  to transfer a set of MIDI data codes to the random access memory  103 , and the MIDI data codes are stored as shown in FIG.  8 . The central processing unit  201  proceeds to step S 33 , and writes the time periods and addresses in the registers D 1 / D 2 / AD 1 / AD 2  as by step S 33 . The first event data “note-on” is stored in address “2”, and the duration time until the first note-on is “100”. The central processing unit  201  subtracts 50 from 100, and writes the difference, i.e., 50 in the register D 1  and the duration data of 100 in the register D 2 . The black/white key  201  assigned the note number  62  is to be sunk for the previous notice and the inductive action, and the note number  62  is stored at address “2”. For this reason, the central processing unit  201  writes the address “2” in both registers AD 1  and AD 2 . This is corresponding to timing t 0  in FIG.  15 . Then, the central processing unit  101  proceeds to step S 34 . 
     On the other hand, if the start switch  141  is not manipulated, the central processing unit  201  skips steps S 32  and S 33 , and proceeds to step S 34 . The central processing unit  101  checks the manipulating switch board  140  to see whether or not the stop switch  142  is manipulated at step S 34 . If the stop switch  142  has been manipulated, the answer at step S 34  is given affirmative, and the central processing unit  101  changes the flag BF to “0” as by step S 35 . Upon completion of step S 35 , the central processing unit returns to the main routine program. On the other hand, if the step switch  142  has not been manipulated, the answer at step S 34  is given negative, and the central processing unit  101  immediately returns to the main routine program without execution of step S 35 . 
     A timer interruption is repeated at intervals equivalent to a single pulse period of the MIDI timing clock signal, and a subroutine program shown in FIG. 12 runs on the central processing unit  101 . The central processing unit  101  firstly checks the random access memory  103  to see whether the flag is “1” or not as by step S 101 . If the guide is not requested (see “NO” at step S 31 ), the answer at step  101  is given negative, the central processing unit  101  immediately returns to the main routine program. 
     On the other hand, if the guide has been requested (see “YES” at step S 31 ), the answer at step S 101  is given affirmative, and the central processing unit  101  decrements the duration time stored in the register D 1  and the duration time stored in the register D 2  as by step S 102 . 
     Subsequently, the central processing unit  101  checks the register D 1  to see whether or not the duration time reaches zero as by step S 103 . If the answer at step S 103  is given negative, the central processing unit  101  checks the register D 2  to see whether or not the duration time reaches zero as by step S 104 . If the answer at step S 104  is given negative, the central processing unit  101  returns to the main routine program. Thus, the central processing unit  101  decrement the duration times stored in the registers D 1 /D 2  at every clock pulse of the MIDI timing clock signal. 
     After repetition of the timer interruption, the duration time stored in the register D 1  reaches zero at step S 102 , and the answer at step S 103  is given affirmative. Then, the central processing unit  101  decides that the timing to give the previous notice comes, and is branched to a subroutine for a previous notice at step S 110 . 
     A subroutine program for a previous notice is shown in FIG.  13 . The central processing unit  101  reads out the address from the register AD 1  as by step S 111 , and determines a black/white key  201  assigned the note number to be sunk for the previous notice. The address “2” is stored in the register AD 1 , and the MIDI data code is indicative of the note number “62”. The note number “62” is indicative of the white key “D”. Subsequently, the central processing unit  101  supplies a control signal Ss to the controller  221 , and the controller  221  causes the power transistor  222  associated with the black/white key  201  to turn on. The key drive unit  230  under the black/white key  201  is energized, and pushes up the rear end portion of the black/white key  201 . Then, the front end of the black/white key assigned the note number is sunk by Ls, and gives the previous notice to the trainee as by step S 112 . 
     Subsequently, the central processing unit  101  searches the random access memory  103  for the next note-on event. The next note-on event is instructed by the MIDI data code stored at the address “6”. Then, the central processing unit  101  rewrites the register AD 1  from address “2” to address “6” as by step S 113 . This is corresponding to timing t 1  in FIG.  15 . Thereafter, the central processing unit  101  returns to the subroutine program shown in FIG.  12 . 
     The central processing unit  101  repeats the decrement of the duration time stored in the register D 2 , and the duration time finally reaches zero. Then, the answer at step S 104  is given affirmative, and the central processing unit  101  is branched to a subroutine for the inductive action as by step S 120 . FIG. 14 shows a subroutine program for the inductive action. The central processing unit  101  firstly removes the previous notice from the white key D as by step S 121 . Subsequently, the central processing unit  101  determines a duration time until the next previous notice, and writes the duration time in the register D 1  as by step S 122 . The next note-on event takes place at the white key assigned the note number  67  represented by the MIDI data code stored at address “6”. The total duration time is 500, i.e., 200+300, and the central processing unit  101  subtracts 50 from 500. The duration time until the next previous notice is 450. Thus, the central processing unit  101  writes 450 in the register D 1 . 
     Subsequently, the central processing unit  101  reads out the MIDI data code from the register AD 2  as by step S 123 , and checks the MIDI data code to see whether or not the note-on is requested as by step S 124 . The address “2” is stored in the register AD 2 , and the MIDI data code stored at the address “2” is indicative of the note-on. Then, the answer at step S 124  is given affirmative, and the central processing unit  101  proceeds to step S 125 . The central processing unit  101  supplies the control signal Ss representative of the inductive action to the controller  221 . The controller  221  causes the power transistor  222  associated with the white key D to turn on, and the electric power source  210  energizes the key driver unit  230  under the white key D. The white key D is sunk by the short stroke Ls, and gives the inductive action to the trainee. 
     Subsequently, the central processing unit  101  searches the random access memory  103  for the next duration time and the next event date. The next duration data is store at address “3”, and is  200 . The next event data is stored at address “4”. Then, the central processing unit  101  writes the duration data of “200” and the next address “4” in the register D 2  and the register AD 2  as by step S 127 . Thereafter, the central processing unit  101  returns to the subroutine shown in FIG.  12 . The trainee depresses the white key D, and the tone is generated. 
     When the duration time in the register D 2  reaches zero, again, the answer at step S 124  is given negative, because the event data stored at the address “4” is the note-off. The central processing unit  101  instructs the controller  221  to change the power transistor  222  to the off-state, and the key driver unit  230  retracts the plunger into the solenoid. Then, the inductive action is removed from the white key D as by step S 126 , and the white key D is allowed to return to the rest position. 
     Subsequently, the central processing unit  101  searches the random access memory  103  for the next duration time and the next event date. The next duration data is store at address “5”, and is  300 . The next event data is stored at address “6”. Then, the central processing unit  101  writes the duration data of “300” and the next address “6” in the register D 2  and the register AD 2  as by step S 127 . This is corresponding to timing t 3 . Thereafter, the central processing unit  101  returns to the subroutine shown in FIG.  12 . 
     Thus, the central processing unit  101  repeats the subroutine for the guide, and the electric tutor gives the previous notice and the inductive action to the trainee, and guides him in the practice on the acoustic piano  200 . The next previous notice is given at timing t 4 , and the next inductive action is given at timing t 5 . Even if the trainee does not depress the white key G, the inductive action is removed from the white key G at timing t 6 . Although any MIDI data code for the damper pedal  202  is not incorporated in the part of the set of MIDI data codes shown in FIG. 8, the central processing unit  101  gives the previous notice and the inductive action to the trainee for the damper pedal  202 . 
     As will be understood from the foregoing description, the electric tutor gives the previous notice to the trainee fifty clock pulses before the timing to depress a black/white key  201 , removes the previous notice, and gives the inductive action to the trainee at the timing to depress the black/white key  201 . The previous notice and the inductive action are given to the trainee as the short stroke Ls of the black/white key  201 . The stroke Ls is too short to make the jack of the key action mechanism  205  escape from the hammer  253 , and any acoustic/electronic tone is not generated. If the tempo is 60, the fifty clock pulses are equivalent to 50/24 second. The time interval between the previous notice and the inductive action is long enough to make the trainee ready for depressing the black/white key  201 . The trainee follows the inductive action, and depresses the black/white key  201  for generating the acoustic/electronic tone. The trainee needs to pay the attention to the fingers without the music score, and the electric tutor effectively guides the practice on the acoustic piano  200 . 
     In the first embodiment, the floppy disk and the random access memory  103  form in combination a memory. The central processing unit  101 , the computer programs shown in FIGS. 11,  12 ,  13  and  14  and the registers D 1 /D 2 /AD 1 /AD 2  as a whole constitute a data processor. The controller  220 , the power transistors  222 / 223 , the key driver units  230  and the pedal driver unit  260  as a whole constitute a driver. The black/white keys  201  and the damper pedal  202  serve as plural manipulators, and the key action mechanisms  205 , the hammers  253 , the sets of strings  290  and the electronic tone generating system as a whole constitute a tone generating means. 
     Second Embodiment 
     Another electronic piano embodying the present invention is similar in structure to the first embodiment, and only the software for the electric tutor is different. The electric tutor of the first embodiment gives the previous notice and the inductive action through the black/white key  201  to be depressed to the trainee. The electric tutor of the second embodiment further instructs a direction from a presently depressed black/white key  201  to the next black/white key  201 . In order to instruct a finger from the presently depressed black/white key  201  to the next black/white key  201  to be depressed, the electric tutor successively sinks the black/white keys  201  therebetween by the short stroke Ls. In the following description, a set of MIDI data codes used in the training is assumed to be identical with that shown in FIG.  8 . 
     Description is focused on registers not used in the first embodiment and, thereafter, computer programs different from those of the first embodiment. As described hereinbefore, the registers D 1 , D 2 , AD 1  and AD 2  are used for the electric tutor in the first embodiment. Registers D 3  and H are further used for the electric tutor of the second embodiment. The register D 3  is assigned to a piece of control data information representative of a time period until the instruction for movement, and the register H is assigned to another piece of control data information representative of the direction from the presently depressed black/white key  201  to the next black/white key  201  to be depressed. The note numbers assigned to the intermediate black/white key are sequentially stored in the register H for the instruction for movement. 
     FIG. 16 illustrates a subroutine program executed at every timer interruption, and is corresponding to the subroutine shown in FIG.  12 . The duration times “50”, “100” and “0” and the addresses “2”, “2” and zero have been stored in the registers D 1 /D 2 /D 3  and AD 1 /AD 2 / H, respectively, as shown in FIG.  17 . 
     When the timer interruption takes place, the central processing unit  101  firstly checks the random access memory  103  to see whether or not the flag BF is “1” as by step S 201 . If the electric tutor has not been requested to guide the trainee, the answer at step S 201  is given negative, and the central processing unit  101  immediately returns to the main routine program. On the other hand, if the electric tutor is requested to guide the trainee in the practice on the acoustic piano  200 , the flag was changed to “1” (see S 32  in FIG.  11 ), and the answer at step S 201  is given affirmative. Then, the central processing unit  101  decrements the duration times stored in the registers D 1 /D 2 /D 3  by one as by step S 202 . As described hereinbefore, the duration time stored in the register D 1  is indicative of a time period until the previous notice, and the duration time stored in the register D 2  is indicative of a time period until the inductive action. The duration time stored in the register D 3  is indicative of a time period until the instruction for movement. The timer interruption takes place at the intervals of a pulse period of the MIDI timing pulse signal, and the duration times are decremented by one clock pulse during each timer interruption. When the duration times reach zero, the electric tutor starts to give the previous notice, the inductive action and the indication of direction to the trainee. In other words, the duration times stored in the registers D 1 /D 2 /D 3  give the timings to start the previous notice, the inductive action and the instruction for movement to the electric tutor. 
     Subsequently, the central processing unit  101  sequentially checks the registers D 1 /D 2 /D 3  to see whether or not any one of the duration times reaches zero as by step S 203 , S 205  and S 208 . If all the answers are given negative, the central processing unit  101  returns to the main routine program. The central processing unit  101  repeats the subroutine program at intervals of the pulse period of the MIDI timing clock signal, and sequentially checks the registers D 1 /D 2 /D 3  for the timings. 
     When the duration time stored in the register D 1  reaches zero, the answer at step  203  is given affirmative, and the central processing unit  101  proceeds to a subroutine for the previous notice. This is corresponding to timing to in FIG.  17 . The central processing unit  101  executes the subroutine program shown in FIG.  13 . The central processing unit  101  determines the white key D assigned the note number  62  to be sunk for the previous notice on the basis of the MIDI data code stored in the address “2”. The white key D is sunk by Ls for the previous notice, and the address stored in the register D 1  is changed from “2” to “6”. 
     The answer at step S 205  is changed to affirmative at timing t 2  (see FIG.  17 ), and the central processing unit  101  proceeds to the subroutine for the inductive action. The subroutine program shown in FIG. 14 runs on the central processing unit  101 . The previous notice is removed from the white key D, and the duration time in the register DI is changed to “450”. The inductive action is given to the white key D, and the central processing unit  101  changes the duration time in the register D 2  and the address in the register AD 2  from “0” to “200” and from “2” to “4”. 
     Subsequently, the central processing unit  101  makes ready for the instruction for movement as by step S 207 . The central processing unit  101  calculates the time period until the instruction for movement, and stores a duration time corresponding to the time period in the register D 3 . The central processing unit  101  stores the note number assigned to the white key D in the register H. 
     The time period until the instruction for the movement is calculated as follows. As described hereinbefore, the previous notice is given fifty clock pulses before the timing to depress the next black/white key  201 . In this instance, the next black/white key  201  to be depressed is the white key G, and the white key G is to be depressed at timing t 9 . The previous notice is to be given at timing t 8 . For this reason, the electric tutor has to sequentially sink the black/white keys D#, E, F and F# between timing t 2  and timing t 8 . The electric tutor changes the intervals between the black/white keys to be sunk depending upon the number of the black/white keys  201  between the presently depressed black/white key  201  and the next black/white key  201  to be depressed. If there are many black/white keys  201 , the electric tutor sequentially sinks the black/white keys  201  at short intervals. On the other hand, if there are only a few black/white keys  201 , the electric tutor sequentially sinks the black/white keys  201  at long intervals. Thus, the electric tutor informs the trainee of the distance between the presently depressed black/white key  201  and the next black/white key  201  to be depressed by changing the intervals. 
     The central processing unit  101  firstly calculates a time period Ta from the timing to presently depress the black/white key  201  to the timing for the next previous notice. Subsequently, the central processing unit  101  determines the number N of black/white keys  201  on the basis of the note number assigned to the presently depressed black/white key  201  and the note number assigned to the next black/white key  201  to be depressed. The time intervals Tb are calculated as 
     
       
         Tb=Ta/N 
       
     
     The presently depressed black/white key  201  is the white key D, and the next black/white key  201  to be depressed is the white key G. The total duration time is 500, i.e., 200+300 (see addresses “2” and “5”). The previous notice is fifty clock pulses before the inductive action for the white key G, and the time period Ta is 450. The note number assigned to the white key D is 62, and the note number assigned to the white key G is 67, Then, the number N of black/white keys  201  is 5, i.e., 67-62. The time intervals Tb is calculated at 90. For this reason, the duration time “90” is stored in the register D 3  (see timing t 2  in FIG.  17 ). 
     The central processing unit repeats the subroutine program, and waits for a change of answer at step S 208 . The duration time stored in the register D 3  reaches zero at timing t 3 , and the answer at step S 208  is changed to affirmative. Then, the central processing unit  101  proceeds to step S 210 , and executes a subroutine for the instruction for movement. FIG. 18 shows a subroutine program for the instruction for movement. The central processing unit  101  firstly causes the black/white key  201  assigned the note number stored in the register H to return to the rest position as by step  211 . 
     Subsequently, the central processing unit  201  compare the MIDI data code stored at the address stored in the register AD 2  and the note number stored in the register H to see whether or not the next black/white key  201  to be depressed is located on the right side of the presently depressed/sunk black/white key  201  as by step S 212 . If the answer at step S 212  is given affirmative, the central processing unit  201  increments the note number by one as by step S 213 . On the other hand, if the answer at step S 212  is given negative, the central processing unit  201  decrements the note number by one as by step S 214 . However, if the next black/white key  201  is same as the presently depressed black/white key  201 , the central processing unit  101  immediately returns to the subroutine program, because any instruction for movement is not required. In this instance, the presently depressed black/white key  201  is the white key D assigned the note number “62”, and the next black/white key  201  to be depressed is the white key G assigned the note number “67”. Then, the central processing unit  201  increments the note number stored in the register H. As a result, the note number “63” is stored in the register H (see timing t 3 ). 
     Subsequently, the central processing unit  201  supplies the control signal Ss to the controller  211  so as to energize the power transistor  222  associated with the black/white key  201  assigned the note number stored in the register H. Then, the key drive unit  230  sinks the adjacent black/white key  201  by the short stroke Ls as by step S 215 . 
     Subsequently, the central processing unit  101  stores the duration time or the time interval “90” in the register D 3 , again, as by step S 216 , and returns to the subroutine program shown in FIG.  16 . 
     The central processing unit  101  repeats the timer interruption, and decrements the duration time stored in the register D 3 . The duration time stored in the register D 3  reaches zero at timing t 4 , again. Then, the central processing unit  201  instructs the driver  221  to remove the potential from the key driver unit  230  under the key D# and to actuate the key driver unit  230  under the key E. The key D# returns to the rest position, and the key driver unit  230  sinks the key E by the stroke Ls. The central processing unit  101  rewrites the note number stored in the register H and the duration time stored in the register D 3  to “64” and “90”, respectively. 
     Similarly, the black/white keys F and F# are sunk at timing t 6  and timing t 7 , respectively, at the intervals of “90”. The black/white keys D#, E, F and F# are sequentially sunk by the short stroke Ls, and the electric tutor instructs the trainee that the next white key G to be depressed is on the right side of the presently depressed white key D. The electric tutor gives the previous notice to the trainee at time t 8 , and the inductive action to the trainee at time t 9  for the white key G. 
     As will be understood from the foregoing description, the electric tutor implementing the second embodiment gives a trainee the instruction of movement as well as the previous notice and the inductive action. The trainee is previously noticed which direction he has to move the hand. Moreover, the time intervals to sequentially sink the black/white keys are varied depending upon the interval between the presently depressed key and the next key. The trainee is further noticed how fast he has to move the hand. Thus, the electric tutor according to the present invention guides the trainee in the practice on the acoustic piano. 
     Although particular embodiments of the present invention have been shown and described, it will be obvious 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. 
     For example, the acoustic piano may be a standard grand piano. The hammer stopper may be changed between the free position and the blocking position by an electric motor, and the control unit  100 A may instruct a driver to energize the electric motor. 
     The electric tutor may be provided for another kind of keyboard musical instrument such as, for example, an electronic keyboard, an acoustic upright piano, an acoustic grand piano, an organ and a harpsichord and another kind of musical instrument such as, for example, a wind instrument and a stringed instrument as long as the musical instrument has plural manipulators used for a performance. 
     The electric tutor may give the previous notice and the induced action to a trainee for other pedals, i.e., the soft pedal and a sostenute pedal. 
     The set of digital data codes may be transferred from another kind of information storage medium such as a CD-ROM, an opto-magnetic disk. Sets of digital data codes may be built in a hard disk. A set of digital data codes may be supplied from an external source through a communication line to the random access memory  103 . A set of digital data codes may represent an actual performance on the acoustic piano  200 . In this instance, the central processing unit  101  instructs the floppy disk driver  110  to store it in a floppy disk or another kind of information storage medium. 
     The digital data codes may be formed on the basis of another kind of standards. The lapse of time to an event may be stored in the form of absolute time or in the form of note. 
     Acoustic tones may be produced in the practice guided by the electric tutor. An electric tutor may slightly lift black/white keys to be depressed. If the electronic tones are generated in the practice guided by the electric tutor, the stroke Ls may be equal to the stroke Lh. In this instance, the key motions for the previous notice and the inductive action are ignored, and no electronic tone is generated. Otherwise, the sets of strings are blocked from the hammers. 
     In the above-described embodiments, term “initial position” is corresponding to the rest position of the black/white key  201 , However, if a grand piano is used as the acoustic piano  200 , the initial position may be corresponding to a home position of a jack not actuated by the associated black/white key, because the trainee can depress the black/white key in so far as the jack button and the jack stop spoon are in contact. 
     The electric tutor may keep the black/white keys between the presently depressed key and the next key in the depressed state until the previous notice for the next key. The time interval may be shortened toward the next key. The interval between the previous notice and the inductive action are not limited to 50 clock pulses, and the timing clock. The interval may be given as an absolute time period. The timing clock is not limited to the MIDI timing clock signal. 
     One of the previous notice and the inductive action may be given through an array of light emitting diodes provided on or in proximity to the black/white keys to be depressed. In this instance, the controller  221  selectively energizes the light emitting diodes as well as the key drive units  230  for the inductive action. The light emitting diodes between the presently depressed key and the next key to be depressed may be sequentially energized for radiating light beams for the instruction for movement. The array of light emitting diodes may be provided on the black/white keys or in the proximity to the black/white keys. The light emitting diodes may be replaced with other light-emitting elements or a liquid crystal display. The light emitting elements may be changed between on-state and off-state or between a color and (red) a different color (green). The light-emitting elements or the liquid crystal display serve as indicators. 
     The computer programs may be transferred from a non-volatile memory card, a CD-ROM, a floppy disk, an opto-magnetic disk or a magnetic disk to the random access memory  103 . Such a portable information storage medium is convenient at a version-up.