Patent Publication Number: US-5831194-A

Title: Electronic keyboard musical instrument capable of imparting effect similar to that of soft pedal

Description:
FIELD OF THE INVENTION 
     This invention relates to an electronic keyboard musical instrument and, more particularly, to an electronic keyboard musical instrument capable of imparting an effect similar to the effect of the soft pedal of an acoustic piano. 
     DESCRIPTION OF THE RELATED ART 
     A pianist not only selectively fingers the keys on the keyboard but also steps on pedals so as to change the piano sounds. When the pianist steps on the damper pedal, the dampers are hold over the strings after release of the depressed keys, and prolong the piano sounds. The soft pedal causes the hammers to strike the strings smaller in number than those without the step-on of the soft pedal, and lessens the loudness of the piano sounds. The effects imparted by the damper pedal and the soft pedal are hereinbelow referred to as &#34;damper effect&#34; and &#34;soft effect&#34;, respectively. 
     An electronic keyboard musical instrument is designed to allow a player to give similar effects to the electronic sounds. When a player steps on the damper pedal of the electronic keyboard musical instrument, the tone generator changes the sustain of the envelop for electronic sounds, and retards the extinguishment of the electronic sound. Thus, the damper effect is easily realized by simply prolonging the sustain of the envelop. 
     On the other hand, the soft effect is hardly realized by the electronic keyboard musical instrument. This is because of the fact that the soft effect of an acoustic piano is complex. As described hereinbefore, when a pianist steps on the soft pedal of an acoustic piano, the hammer strikes a smaller number of strings than usual. The vibrations of the smaller number of strings are gently decayed, and, accordingly, the piano sound is prolonged. However, the soft effect is not limited to the prolongation of the acoustic sound. The smaller number of strings slightly increase the frequency of vibrations, and, accordingly, slightly lifts the pitch of the piano sounds. Thus, the soft effect is complex, and the prior art electronic keyboard musical instrument can not presently impart the complicated soft effect to the electronic sounds. 
     SUMMARY OF THE INVENTION 
     It is therefore an important object of the present invention to provide an electronic keyboard musical instrument which allows a player to impart the complicated soft effect to electronic sounds. 
     To accomplish the object, the present invention proposes to sequentially read out pieces of waveform data at a certain speed higher than usual. 
     In accordance with the present invention, there is provided an electronic keyboard musical instrument comprising a keyboard having a plurality of keys selectively depressed by a player for specifying a note of an electronic sound, a pedal depressed by the player for imparting predetermined effects to the electronic sound and a tone generator responsive to one of the plurality of keys depressed by the player for producing the electronic sound, and the tone generator is further responsive to the aforesaid one of the plurality of keys and the pedal depressed by the player for not only slightly increasing the pitch of the electronic sound but also decreasing the loudness of the electronic sound. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantages of the electronic keyboard musical instrument according to the present invention will be more clearly understood from the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram showing an electronic keyboard musical instrument according to the present invention; 
     FIG. 2 is a block diagram showing the circuit arrangement of a tone generator incorporated in the electronic keyboard musical instrument; 
     FIG. 3 is a block diagram showing the circuit arrangement of a tone generator incorporated in another electronic keyboard musical instrument according to the present invention; 
     FIG. 4 is a graph showing waveforms of an electric signal differently tailored depending upon a step-on of a soft pedal; and 
     FIG. 5 is a graph showing a gain in terms of the frequency component of an analog audio signal in a filter circuit of the tone generator. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
     Referring first to FIG. 1 of the drawings, an electronic keyboard musical instrument embodying the present invention comprises a keyboard 1a, a damper pedal 1b and a soft pedal 1c. The electronic keyboard musical instrument is called an &#34;electronic piano&#34;, and the keyboard 1a and the pedals 1b/1c correspond to those of an acoustic piano. The keyboard la is supported by a case (not shown), and laterally extends in front of a player sitting on a chair (not shown). The keyboard has a plurality of black and white keys 1d/1e arranged similar to the keyboard of an acoustic piano, and the plurality of black and white keys 1d/1e are respectively associated with key switches 1f so as to detect a change of key status. The key switches 1f are closed or opened by the associated keys 1d/1e, respectively, and the matrix of key switches 1f produces key status signals KS each representative of the current key status of the associated key 1d/1e. Notes of a scale are respectively assigned to the black and white keys 1d/1e, and the player selectively specifies the notes by depressing the keys 1d/1e. The notes respectively assigned to the keys 1d/1e are identified with key codes, respectively. 
     The damper pedal 1b and the soft pedal 1c project from a lower portion of the case, and the player can step on the damper pedal 1b and the soft pedal 1c. The damper pedal 1b and the soft pedal 1c are also associated with pedal switches 1g, and the pedal switches 1g monitors the damper pedal 1b and the soft pedal 1c to see whether or not the player steps on the damper pedal 1b or the soft pedal 1c. The pedal switches 1g produce pedal status signals PS each representative of the current pedal status of the associated one of the damper pedal 1b and the soft pedal 1c. 
     The electronic keyboard musical instrument further comprises a music data processing system 2 and a sound system 3. The music data processing system 2 periodically scans the keyboard 1a and the damper/soft pedals 1b/1c to see whether or not the player manipulates the black and white keys 1d/1e and the damper/soft pedals 1b/1c. When the player depresses and, thereafter, releases a key 1d/1e, the music data processing system 2 tailors an analog audio signal AD through a digital data processing, and supplies the analog audio signal AD to the sound system 3. 
     The music data processing system 2 can modify the analog audio signal AD in response to the damper pedal 1b. However, the signal processing for the damper pedal 1b is similar to that of the prior art, and description is focused on a signal processing for the soft pedal 1c. 
     The sound system 3 includes an amplifier and speakers. The amplifier increases the amplitude of the analog audio signal AD to a range specified by the player, and the speakers produce an electronic sound with the note assigned the depressed/released key 1d/1e from the analog audio signal AD. 
     The music data processing system 2 includes a read only memory 2a, a random access memory 2b, a central processing unit 2c, a tone generator 2d and a manipulating panel 2e, and these component units 2a to 2e are connected through a shared bus 2f. 
     Though not shown in FIG. 1, a suitable signal interface is connected between the shared bus 2f and the matrix of key switches 1g/pedal switches 1g, and the central processing unit 2c periodically checks the signal interface to see whether or not the matrix of key switches 1f and/or the pedal switches 1g change the key status signal KS and/or the pedal status signal PS1. When the central processing unit 2c acknowledges a change of key status, the central processing unit generates a music data codes or codes MDC1 representative of at least key code and the current key status, i.e., key-on status or key-off status. On the other hand, when the pedal switches 1g informs the central processing unit 2c of a change of pedal status, the central processing unit 2c generates a music data code MDC2. If the pedal status signal PS informs the central processing unit 2c of the change of pedal status of the soft pedal 1c, the music data code MDC2 represents at least the soft pedal 1c and the bend indicative of an increment of pitch. Thus, the central processing unit 2c successively generates the music data codes MDC1 and MDC2 during a performance, and transfers the music data codes MDC1 and MDC2 to the tone generator 2d. 
     The read only memory 2a stores not only a program sequence executed by the central processing unit 2c but also pieces of standard pitch data information. The pieces of standard pitch data information are representative of standard pitches for the notes of the scale assigned to the electronic sounds. The standard pitches may be modified by the player, and the modified pitches are stored in the random access memory 2b. The central processing unit 2c transfers the pieces of pitch data information representative of the standard pitches or the modified pitches from the read only memory 2a or the random access memory 2b to the tone generator 2d before starting a performance. 
     Various switches are provided on the manipulating panel 2e. One of the switches is a power supply switch. The player connects the music data processing system 2 and the sound system 3 to an external power source and cuts the electric power by manipulating the power supply switch. Another switch is a volume control switch. The player varies the loudness of the electronic sounds by using the volume control switch. Yet another switch is used for selecting a timbre from the candidates. 
     FIG. 2 illustrates the circuit arrangement of the tone generator 2d incorporated in the music data processing system 2. The tone generator 2d includes a phase information generating circuit 2da, a waveform memory 2db, a filter circuit 2dc and an envelop generator 2de. The music data codes MDC1/MDC2 are supplied to the phase information generating circuit 2da, and the analog audio signal AD is supplied from the envelop generator 2de to the sound system 3. 
     The waveform memory 2db stores pieces of waveform information, and the envelop generator 2de tailors the analog audio signal AD on the basis of the pieces of waveform information. The sound generating process is called as &#34;waveform memory read-out technology&#34;. 
     The waveform memory read-out technology is briefly described. Acoustic sounds were previously sampled, and the sampled waveform data were digitized so as to store the waveform memory 2db. A set of digital waveform data codes is representative of the waveform of an acoustic sound, and a plurality of sets of digital waveform data codes are respectively provided for the notes of the electronic sounds in a certain timbre. As described hereinbefore, the electronic keyboard musical instrument can give various timbres to the electronic sounds, and a set of digital waveform data codes are stored for each of the timbres selectable through the manipulating panel 2e. When the player depresses one of the black and white keys 1d/1e, the central processing unit 2c instructs the tone generator 2d to sequentially read out the digital waveform data codes from the read only memory 2a in response to a tempo clock signal corresponding to the pitch of the note specified by the depressed key 1d/1e. 
     The central processing unit 2c teaches the key code assigned to a depressed key 1d/1e through the music data code MDC1 to the phase information generating circuit 2da. When the player steps on the soft pedal 1c, the central processing unit 2c further teaches the bend indicative of an increment of pitch through the music data code MDC2 to the phase information generating circuit 2da. The phase information generating circuit 2da produces pieces of phase data information from the key code and the bend, and supplies the piece of phase data information to the waveform memory 2db. 
     As described hereinbefore, the waveform memory 2db stores the plurality of sets of waveform data codes each representative of the waveform of an acoustic sound, and one of the sets of waveform data codes corresponds to the electronic sound to be produced in response to the depressed key 1d/1e. The tone generator 2d selects a set of waveform data codes depending upon the key code, and the selected set of waveform data codes specifies a series of discrete values from the rise to the decay. The waveform data codes of the selected set are sequentially read out from the waveform memory 2db through the filter circuit 2dc to the envelop generator 2de, and the envelop generator 2de tailors the analog audio signal AD on the basis of the series of discrete value. If the read-out speed of the waveform data codes of the selected set is increased, the pitch of the electronic sound is changed. 
     The filter circuit 2dc is an active filter, and eliminates high frequency components from the waveform data information represented by the waveform data codes. 
     The envelop generator 2de multiplies the discrete value of the waveform data code by a certain value represented by an envelop signal so as to give a selected envelop to the analog audio signal AD. The envelop is usually divided into an attack immediately after depressing a key 1d/1e, a decay for a sustain and a release at release of the depressed key 1d/1e. Thus, the envelop generator 2de gives the envelop to the analog audio signal AD, and the sound system 3 produces the electronic sound in the selected timbre. 
     Assuming now that the player depresses one of the black and white keys 1d/1e and concurrently steps on the soft pedal 1c, the matrix of key switches if supplies the key status signal KS representative of the change of key status from the key-off to the key-on for the depressed key 1d/1e to the signal interface, and the pedal switch 1g supplies the pedal status signal PS representative of the step-on of the soft pedal 1c to the signal interface. 
     The central processing unit 2c identifies the depressed key 1d/1e, and produces the music data code MDC1 representative of the key code and the change of key status from the key-off to the key-on. The central processing unit 2c further produces the music data code MDC2 representative of the step-on of the soft pedal 1c and the bend. 
     The central processing unit 2c teaches the key code and the bend to the phase information generating circuit 2da. The standard/modified pitch data information has been already transferred to the phase information generating circuit 2da, and the phase information generating circuit 2da forms a piece of composite phase data information from the piece of standard/modified pitch data information selected by using the key code and the increment of pitch represented by the bend. The piece of composite phase data information is indicative of a read-out speed for the waveform data codes of a selected set, and the bend increases the read-out speed rather than a read-out speed without the step-on of the soft pedal 1c. 
     The phase information generating circuit produces an address signal ADD on the basis of the piece of composite phase data information, and sequentially increments the address represented by the address signal ADD at the read-out speed. 
     The address signal ADD is supplied to the waveform memory 2db, and the waveform data codes are sequentially read out from the waveform memory 2db faster than waveform data codes specified without the step-on of the soft pedal 1c. The waveform data codes sequentially pass through the filter circuit 2dc, and are supplied to the envelop generator 2de so as to tailor the analog audio signal AD. 
     The central processing unit 2c may instruct the envelop generator 2de to slightly decrease the loudness of the electronic sound under the manipulation of the soft pedal 1c. 
     As described hereinbefore, if waveform data codes of a selected set are read out from the waveform memory 2db faster than usual, the electronic sound becomes higher in pitch. For this reason, the electronic sound is slightly higher in pitch than an electronic sound produced without the step-on of the soft pedal 1c. If the piece of standard pitch information is indicative of 400 Hz, the bend causes the phase information generating circuit 2da to increase the read-out speed at 0.05 percent, and the sound system 3 produces the electronic sound at 440.2 Hz. 
     Thus, the tone generator 2d slightly increase the pitch of the electronic sound, and the music data processing system 2 according to the present invention imparts the effects similar to those of the soft pedal of an acoustic piano to the electronic sounds. 
     Second Embodiment 
     Another electronic keyboard musical instrument embodying the present invention has an arrangement similar to that of the first embodiment shown in FIG. 1 except for a tone generator 12d shown in FIG. 3, and the other components are specified by using the same references as those of the first embodiment in the following description. 
     The tone generator 12d includes a waveform data supplier 12da, an envelop generator 12db, a multiplier 12dc, a filter circuit 12dd and a volume controller 12de. The waveform data supplier 12da may correspond to the phase information generating circuit 2da and the waveform memory 2db. The envelop generator 12db is responsive to the music data code MDC representative of the key code so as to produce an envelop signal, and controls the loudness and the duration of an electronic sound. 
     The music data code MDC representative of the key code is supplied to both of the waveform data supplier 12da and the envelop generator 12db, and the music data code MDC2 representative of the step-on of the soft pedal 1c is supplied to the waveform data supplier 12da, the envelop generator 12db, the filter circuit 12dd and the volume controller 12de. A series of waveform data codes are multiplied by envelop data at the multiplier 12dc, and an analog audio signal AD is supplied to the filter circuit 12dd. 
     The filter circuit 12dd is responsive to the music data code MDC2 so as to eliminate high-frequency components from the analog audio signal 12dd, and the loudness of the volume control 12de is regulated by the volume control 12de. 
     Assuming now that a player steps on the soft pedal 1c during a performance, the central processing unit 2c acknowledges the step-on of the soft pedal 1c through the pedal status signal PS, and identifies a key or keys 1d/1e depressed during the step-on of the soft pedal 1c. The central processing unit 2c supplies the music data code MDC1 representative of the key code assigned to the depressed key 1d/1e to the waveform data supplier 12da and the envelop generator 12db, and informs the waveform data supplier 12da, the envelop generator 12db, the filter circuit 12dd and the volume control 12de of the step-on of the soft pedal 1c. 
     The waveform data supplier 12da outputs a series of waveform data codes at a certain speed higher than usual as similar to the waveform memory 2db, and the envelop generator outputs the envelop data representative of a gentle envelop as indicated by plots PL1 in FIG. 4. When the soft pedal 1c is not depressed, the envelop generator 12db outputs the envelop data representative of a steep envelop indicated by plots PL2. The envelop PL1 has a gentle attack, and the peak of the gentle envelop is lower than the peak of the steep envelop PL2. The gentle envelop PL1 is smaller in decay angle than the steep envelop PL2, and the gentle envelop PL1 is prolonged rather than the steep envelop PL2. Thus, the envelop generator 12db supplies the gentle envelop PL1 to the multiplier 12dc so as to decrease the loudness and prolong the duration under the step-on of the soft pedal 1c. 
     The multiplier 12dc multiplies the series of the waveform data codes by the envelop data representative of the gentle envelop PL1, and forms the analog audio signal AD. 
     The filter circuit 12dd is responsive to the music data code MDC2 representative of the step-on of the soft pedal 1c so as to enhance the quality factor. When the quality factor is enhanced, the high frequency components of the analog audio signal AD is widely cut off, and a certain frequency range is emphasized as will be understood from plots PL3 in FIG. 5. Plots PL4 represents the filtering characteristics without a step-on of the soft pedal 1c. Thus, the soft pedal 1c causes the filter circuit 12dd to emphasize a sound component in the certain frequency range of the electronic sound. 
     The volume control 12de is also responsive to the music data code representative of the step-on of the soft pedal 1c so as to slightly decrease the loudness of the electronic sound. 
     The analog audio signal AD treated in this way is supplied to the sound system 3, and the sound system 3 produces the electronic sound similar to the piano sound produced under the step-on of the soft pedal of an acoustic piano. 
     In this instance, the waveform data supplier 12da slightly increases the pitch of the electronic sound, and the envelop generator 12db and the filter circuit 12dd modifies the frequency characteristics. As described hereinbefore, the soft pedal of an acoustic piano causes the hammer to strike a smaller number of strings. When a pianist does not step on the soft pedal, the hammer usually strikes three strings. The hammer strikes two strings at different points on the strings under the step-on of the soft pedal. 
     When the three strings are concurrently struck, vibrations take place in the three strings, and the three strings are in-phase. For this reason, the three strings are interfered with one another, and the piano sound is rapidly decayed. In other words, the attenuation energy is so large that the three strings rapidly decays the piano sound. 
     On the other hand, when the pianist steps on the soft pedal, only two strings vibrate, and make the attack of the piano sound small. However, the energy is transferred from the vibrating two strings to the other string during the attenuation, and the attenuation energy of the three strings are smaller than that of the three vibrating strings directly struck by the hammer. This results in a long sustain. This is the reason why the envelop generator 12db provides the gentle envelop to the analog audio signal AD. 
     Moreover, the coupled vibration between the strings and the bridges is widely changed due to the decrease of struck strings and the different impact point. As a result, the amplitude of the vibrations is decreased, and the mechanical impedance of the bridges is enlarged from the aspect on the string side. This is equivalent to a shrinkage of the strings, and the pitch is increased. This is the reason why the waveform data supplier supplies the series of waveform data codes faster than usual. 
     Finally, high-order harmonics are liable to take place in the non-struck string, and high-frequency components are emphasized. This is the reason why the filter circuit 12dd provides a large gain to the certain frequency range of the analog audio signal AD. 
     As will be understood from the foregoing description, the tone generator 12d causes the electronic sound to have a small attack, a long sustain, slightly higher pitch and emphasized high-frequency components. 
     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 tone generator may produce a plurality of electronic sounds equal in pitch in response to a change of key status from the key-off to the key-on. In this instance, when a player steps on the soft pedal 1c, the tone generator slightly increases the pitch of one or more than one electronic sound. The tone generator is assumed to produce three electronic sounds equal in pitch without a step-on of the soft pedal 1c. When the player steps on the soft pedal 1c, the tone generator may slightly increase the pitch of two electronic sounds and keep the pitch of the remaining electronic sound. The composite electronic sound is much closer to the acoustic piano sound produced under the step-on of the soft peal. 
     The increment of the pitch may be different between the groups of keys or between the individual keys. A player may change the increment of the pitch under the step-on of the soft pedal 1c. 
     The present invention may be applied to a synthesizer in which a central processing unit generates synthesized sounds under the control of a sequencer. In this instance, the increment of pitch may be achieved by multiplying a control data representative of a read-out speed for the waveform data by a factor more than 1. The factor may be 1.0005.