US3882751A - Electronic musical instrument employing waveshape memories - Google Patents

Abstract

In an electronic musical instrument, actuation of each key switch produces a key data signal indicative of the identification name of the key switch. A key address code corresponding to this key data signal is stored in a key address code memory. Frequency data corresponding to the fundamental frequencies of musical tones for the respective key switches are stored beforehand in a frequency information memory. The key address code read from the key address code memory is used to read frequency information corresponding to the key address code from the frequency information memory. The frequency information is thereafter counted cumulatively in a counter to produce a waveshape address code successively changing with time. Musical tone waveshape memories are provided for storing waveshapes in time-sampled analog representation. The sampled analog values are successively read out in accordance with the changing waveform address code thereby constructing the waveform. Envelope shapes of the musical tones are stored in time-sampled analog representation in envelope memories. Control signals representing depression and release of a key are produced from the key data signal which is produced by the depression and release of the key. A suitable clock pulse is selected by these control signals to read out the envelope shapes. The read out outputs of the envelope memories are applied to the voltage control terminals of the musical tone waveshape memories to determine the instantaneous amplitude thereby causing the musical tone waveshape memories to produce musical tone waveshapes with desired envelopes. In order to enable a simultaneous reproduction of a plurality of musical tones, the instrument is constructed as a dynamic logic system wherein logical circuits as well as the memories and the counters are used in a time sharing manner.

Description

United States Patent 1191 [451 May 13, 1975 ELECTRONIC MUSICAL INSTRUMENT EMPLOYING WAVESHAPE MEMORIES [75 Inventors: Norio Tomisawa, ll-Iamamatsu;

Yasuji Uchiyama, Hamakita; Takatoshi Okumura, Toshio Takea, both of Hamamatsu, all of Japan [73] Assignee: Nippon Gakki Seizo Kabushiki Kaisha 22 Filed: Dec. 11, 1973 21 App]. 110.; 423,846

[30] Foreign Application Priority Data July 6, 1973 Japan 48-125513 Dec. 14, 1972 Japan 47-125514 Dec. 14, 1972 Japan 47-125515 Dec. 14, 1972 Japan 47-125516 Apr. 13, 1973 Japan 48-41964 July 6, 1973 Japan 48-76397 July 6, 1973 Japan 48-76398 [52] US. Cl. ..84/1.0l;84/1.l;84/l.ll; 84/l.l3; 84/l.l9; 84/125; 84/126; 84/127 [51] Int. Cl.G10h 1/02;GlOh 5/02 [58] Field of Search 84/1.01, 1.03, 1.09-1.11, 84/l.l3, 1.19, 1.22-1.28

[56] References Cited UNlTED STATES PATENTS 2,855,816 10/1958 Olson et a1 84/103 3,305,657 2/1967 Haase 84/].23 3,515,792 6/1970 Deutsch 84/1.03 3,594,487 7/1971 Jones, Jr. 84/1.1 3,610,799 10/1971 Watson 84/101 3,610,805 10/1971 Watson et al.. 84/1.l3

3,697,661 10/1972 Deutsch 84/101 3,740,450 6/1973 Deutsch 84/].24

3,743,755 7/1973 Watson 84/].01

3,755,608 8/1973 Deutsch 84/].01 3,763,364 10/1973 Deutsch et al..... 84/].03 X 3,821,714 6/1974 Tomisawa et al.. 84/].01 X 3,823,390 7/1974 Tomisawa et al.. 84/l.01 X

KEVSOARD I CIRCUIT (ounflk Primary Examiner-Richard B. Wilkinson Assistant ExaminerStanley J. Witkowski Attorney, Agent, or Firm-Ladas, Parry, Von Gehr, Goldsmith & Deschamps 57] ABSTRACT In an electronic musical instrument, actuation of each key switch produces a key data signal indicative of the identification name of the key switch. A key address code corresponding to this key data signal is stored in a key address code memory. Frequency data corresponding to the fundamental frequencies of musical tones for the respective key switches are stored beforehand in a frequency information memory. The key address code read from the key address code memory is used to read frequency information corresponding to the key address code from the frequency information memory. The frequency information is thereafter counted cumulatively in a counter to produce a waveshape address code successively changing with time. Musical tone waveshape memories are provided for storing waveshapes in time-sampled analog representation. The sampled analog values are successively read out in accordance with the changing waveform address code thereby constructing the waveform. Envelope shapes of the musical tones are stored in timesampled analog representation in envelope memories. Control signals representing depression and release of a key are produced from the key data signal which is produced by the depression and release of the key. A suitable clock pulse is selected by these control signals to read out the envelope shapes. The read out outputs of the envelope memories are applied to the voltage control terminals of the musical tone waveshape memories to determine the instantaneous amplitude thereby causing the musical tone waveshape memories to produce musical tone Waveshapes with desired 'envelopes. In order to enable a simultaneous reproduction of a plurality of musical tones, the instrument is constructed as a dynamic logic system wherein logical circuits as well as the memories and the counters are used in a time sharing manner.

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MEMORIES IO 55 AK 5 i ouNTEk WAVESHAPE. MEMQRIES oosz ELECTRONIC MUSICAL INSTRUMENT EMPLOYING WAVESHAPE MEMORIES BACKGROUND OF THE INVENTION This invention relates to an electronic musical instrument and, more particularly, to an electronic musical instrument capable of simultaneously producing a plurality of musical tones respectively having predetermined envelopes. The electronic musical instrument according to the invention comprises memories which store musical tone waveshapes in time-sampled analog representation and memories which store, also in timesampled analog representation, envelope signals for the respective musical tones and is adapted to process key data signals corresponding in time relation to the notes of depressed keys and key address codes representing the notes of the depressed keys by utilizing a principle of dynamic logic for reading the waveshapes from these memories.

Electronic musical instruments of conventional types employ a plurality of oscillators or frequency dividers for providing sound source signals from their outputs. These sound source signals are supplied to a tone-color circuit through key switches by closing thereof, whereupon desired musical tone signals are obtained. The prior art electronic musical instruments therefore require a large number of oscillators or frequency dividers. Besides, the tone-color circuit has an extremely complicated construction. As a result, the musical instrument generally has a complicated and large system for producing required musical tone signals.

Moreover, it was impossible in the prior art electronic musical instruments to obtain musical tone signals having the same wave shapes as those of natural musical instruments. The musical tones reproduced from the prior art electronic musical instruments therefore only resembled natural musical tones to a degree which was far from being satisfactory.

The prior art electronic musical instruments require a plurality of musical tone signal production systems which make theirconstruction further complicated and large.

Again, in the prior art electronic musical instruments, an envelope of a musical tone signal which determines the shape of the rise portion of the musical tone when a selected key is depressed, the sustain portion of the tone and the fall portion of the tone after the key has been released, is provided by a switching circuit utilizing charging and discharging characteristics of a capacitor.

Thus, a musical tone signal having a predetermined envelope has been obtained from the output terminal of the switching circuit by applying thereto a signal having a predetermined amplitude and operating a switch provided in the charging and discharging circuit in response to the operation of a key switch.

However, the above described instrument which utilizes charging and discharging characteristics of a capacitor for obtaining a musical tone signal is incapable of producing a complicated envelope of a natural musical tone which, for example, rises abruptly, then falls somewhat rapidly to a certain level and maintains this level for a certain length of time and falls gradually thereafter. The envelope characteristic of the musical tone signal obtained by the above described prior art instrument is at best a rough simulation of that of a natural musical tone. Further, the prior art system is incapable of changing at will the duration of the rise portion of the envelope which is formed immediately after depression of a key (hereinafter referred to as attack") and that of the fall portion which is formed after releasing of the key (hereinafter referred to as decay").

SUMMARY OF THE INVENTION The electronic musical instrument constructed according to this invention uses a principle which is entirely different from the one used in the above described prior art electronic musical instrument. According to the invention, a key data signal is produced upon depression of a key. A key address code corresponding to this key data signal is stored in key address code memories provided with a plurality of channels and a musical tone waveshape is read out at a frequency corresponding to the stored key address code. Simultaneously, control signals respectively representing depression and release of the key are produced from the key data signals produced by the depression and the release of the key, and the reading of the envelope memory is controlled by these control signals. A plurality of musical tones respectively having predetermined envelopes can be simultaneously produced by multiplying the envelope shape outputs with the musical tone waveshape outputs. In order to enable the inventive electronic musical instrument to reproduce a plurality of musical tones simultaneously, the instrument is constructed as a dynamic logical circuits system wherein the logics, the counters, the memories etc. are used in a time-sharing manner.

It is an object of this invention to provide an electronic musical instrument of a remarkably simplified circuit construction capable of simultaneously producing a plurality of musical tone signals having accurate waveshapes and envelopes.

It is another object of the invention to provide an electronic musical instrument capable of simultaneously reproducing a plurality of musical tone waveshapes by constructing the counters, logical circuits and memories according to a dynamic logic principle so that these counters etc. may be used in a timesharing manner.

It is another object of the invention to provide an electronic musical instrument capable of controlling the entire level of a musical tone in response to the speed of depressing the note identification key for that tone.

It is another object of the invention to provide an electronic musical instrument capable of minimizing wiring required for connecting various units which produce musical tones by virtue of utilization of key data signals representing respective keys in time sequence together with key switches.

It is another object of the invention to provide an electronic musical instrument which successfully eliminates adverse effects of chattering of the key switches.

It is another object of the invention to provide an electronic musical instrument capable of accurately producing a plurality of musical tones corresponding to depressed keys up to a maximum number of tones to be reproduced simultaneously.

It is another object of the invention to provide an electronic musical instrument capable of producing a single pedal tone alone regardless of the number of tones to be reproduced simultaneously by operation of the keys of the manual keyboards.

It is another object of the invention to provide an electronic musical instrument in which frequency information representing the notes of the respective keys is stored beforehand in a storage device, frequency information corresponding to the depressed key is read out, and a musical tone waveshape memory is sampled by a waveshape address code signal which is a cumalative counting output obtained by cumulatively counting this frequency information to produce a desired musical tone waveshape signal.

It is another object of the invention to provide an electronic musical instrument capable of varying the sampling frequency of the musical tone waveshape memory in accordance with the pitch (frequency) of the musical tone.

It is another object of the invention to provide an electronic musical instrument capable of reading out a plurality of complicated envelope shapes in a multiplexed form.

It is another object of the invention to provide an electronic musical instrument capable of producing a plurality of musical tones each of which is of a slightly different pitch from the pitch of the note of the corresponding key.

It is still another object of the invention to provide an electronic musical instrument capable of producing musical tones having frequencies which differ slightly from one another depending upon which of several keyboards is used notwithstanding depression of keys forone and the same note.

Other objects and features of the invention will become apparent from the description made hereinbelow with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one preferred embodiment of the electronic musical instrument according to the invention;

FIGS. 2a through 2d are respectively charts showing clock pulses employed in this embodiment of the electronic musical instrument;

FIGS. 3 and 4 are circuit diagrams showing a key data signal generating device employed in the embodiment;

FIG. 5 is a chart showing the correspondence between the key address codes and key switches;

FIGS. 6A and 6B are graphic diagrams illustrative of relations between first and second key data signals and the opening and closing of break and make contacts;

FIGS. 7a and 7b are circuit diagrams showing logical circuits provided for eliminating a chattering effect produced by the key switches;

FIGS. 8a through 8d are graphic diagrams showing key data signals at respective points in the circuit shown in FIGS. 7a and 7b.

FIG. 9 is a circuit diagram showing a detailed logical circuit of a key assigner employed in the embodiment;

FIG. 10 is a block diagram showing fraction and integer counters;

FIG. 11 is a circuit diagram showing one example of a frequency information memory utilizing a (ROM) operated at a low speed;

FIGS. 12a through 121' are charts explanatory of states of signals appearing at certain points of the frequency information memory shown in FIG. 11;

FIG. 13 is a block diagram showing one example of an envelope counter and a truncate counter employed in the inventive electronic musical instrument;

FIGS. 14a and 14b are graphic diagrams illustrating the reading of an envelope waveshape from the enve' lope memory;

FIG. 15 is a block diagram showing one example of a first percussive counter;

FIG. 16 is a graphic diagram showing a waveshape read from a first percussive memory;

FIG. 17 is a block diagram showing one example of a second percussive counter;

FIGS. 18a and 18b are graphic diagrams showing waveshapes read from the second percussive counter;

FIG. 19 is a block diagram showing one example of a touch response counter;

FIGS. 20a through 20s are graphic diagrams explanatory of a touch response operation operation of the touch response counter shown in FIG. 19;

FIG. 21 is a block diagram showing a clock selector;

FIGS. 22a through 22e are graphic diagrams showing waveshapes appearing at certain points in the clock selector shown in FIG. 21; and

FIGS. 23 through 26 are block diagrams respectively showing other embodiments of the electronic musical instrument according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1 which shows one preferred embodiment of the inventive electronic musical instrument, akeyboard circuit 1 has key switches corresponding to respective keys. Each of the key switches includes a break contact and a make contact. A keydata signal generator 2 comprises a key address code generator which produces key address codes indicative of the notes corresponding to the respective keys successively and repeatedly. The keydata signal generator 2 also comprises a first key data signal generating unit 2a which produces a first key data signal when the break contact of a key switch corresponding to a depressed key is opened and a key address code corresponding to the depressed key is produced. The keydata signal generator 2 further comprises a second key data signal generatingunit 2b which produces a second key data signal when the make contact of the key switch is closed and the key address code corresponding to the depressed key is produced. The first and second key data signals are applied to akey assigner 3. Thekey assigner 3 comprises a key address code generator which operates in synchronization with the above described key address code generator, a key address code memory which is capable of storing key address codes up to the same number as a maximum number of musical tones' to be simultaneously reproduced (e.g. 12 channels as in the present embodiment) and successively and repeatedly outputting these key address codes, a logical circuit which, upon receipt of the first key data signal, applies this first key data signal to the key address code memory for causing it to store the corresponding key address code on the condition that this particular key address code has not been stored in any channel of the memory yet and that one of the channels of the memory is available for storing this key address code, and a logical circuit which generates, upon receipt of the first and second key data signals, a tone response signal TRS, an attack start signal ES, a

Claims (25)

1. An electronic musical instrument comprising a key data signal generator which produces, in response to depression and release of a key, a key data signal corresponding to said key in a given key time period of a cyclically repeating plurality of key time periods, a key assigner including means which produce, upon receipt of said key data signal, a key address code corresponding to said key and means which concomitantly produce control signals indicating the depression and release of said key during said given key time period with respect to each of a number of channels which are portions of said time period shared by a maximum number of tones to be reproduced simultaneously, a musical tone waveshape generator means which produce a musical tone waveshape corresponding to the key address code produced from said key assigner, envelope waveshape generator means which produce an envelope waveshape upon receipt of the control signals from said key assigner and means for imparting said envelope waveshape to said musical tone waveshape, said key assigner, musical tone waveshape generating means and envelope waveshape generator means including shift registers having a number of stages corresponding to said number of channels for time-sharing processing of information in said channels and being driven in synchronization with each other.

2. An electronic musical instrument as defined in claim 1 wherein said key data signal generator produces a first key data signal in response to the opening of a break contact of the depressed key and a second key data signal in response to the closing of a make contact of the depressed key, and wherein said key assigner further comprises means for producing a touch response signal indicating the elapsed time between opening of the break contact and closing of the make contact in response to said first and second key data signals, means for producing an output at a level dependent upon said elapsed time in response to said touch response signal and means for multiplying said level output with said envelope waveshape, whereby a musical tone waveshape accompanied by an enveloped at a level corresponding to the touch time of the key is obtained.

3. An electronic musical instrument as defined in claim 2 wherein said means for producing an output at a level dependent upon said elapsed time comprises a touch response memory storing a waveshape which falls from a first level to a second level and sustains this second level thereafter and a counter which is connected to said touch response memory and which counts a clock pulse upon receipt oF said touch response signal and reads said waveshape from said touch response memory by the counting output thereof.

4. An electronic musical instrument as defined in claim 1 wherein said key data signal generator comprises a key address code generator which receives as its input a clock pulse from a clock oscillator and produces a key address code consisting of a note code representing a note in a block of notes, a block code representing said block of notes and a keyboard code representing a keyboard having the key corresponding to said note, a first decoder which produces, upon receipt of said note code, its output sequentially on a plurality of output lines, a second decoder which produces, upon receipt of said block code and said keyboard code, its output sequentially on a plurality of output lines, a respective key switch operable by each key of said keyboard and having a make contact, the make contacts of the key switches for the keys corresonding to notes in each block of notes being connected in common to a respective AND circuit having two, the output of said first decoder to one of the inputs of said AND circuit of the block to which the depressed key belongs through the make contact provide for the key switch of said block when a key address code corresponding to the key is produced from said key address code generator and, the output of said second decoder the the other input of said AND circuit so as to produce an output from said AND circuit, whereby a key data signal representing in time relation the closing of the make contact of the depressed key is produced.

5. An electronic musical instrument as defined in claim 4 wherein said key switches further comprise respective break contacts, the break contacts of the key switches for the keys corresponding to notes in each block of motes being connected in common by respective common break contact members, a plurality of AND circuits each having two input terminals each and circuit being provided for one of the blocks of the key switch with one input terminal thereof being connected to the common break contact member of its corresponding key switch and the other input terminal thereof being connected to its corresponding output line of said second decoder, means for producing an output of aa logical state O from one of said AND circuits corresponding to the common break contact member to which the key switch of the depressed key belongs by interrupting the output from said first decoder upon opening of the break contact corresponding to the depressed key when a key address code corresponding to the depressed key is produced from said key address code generator and an inverter for inverting the output of a logical state O, whereby a key data signal representing in time relation the opening of the break contact corresponding to the depressed key is produced.

6. An electronic musical instrument as defined in claim 4 wherein said key data signal generator further comprises a delay circuit for delaying the key data signal for one key scanning time and an OR circuit which receives the key data signal and the output of said delay circuit, whereby a key data signal free from a chattering effect of the key switches is produced.

7. An electronic musical instrument as defined in claim 1 wherein said key assigner comprises a key address code memory which stores key address codes in channels of a number equal to a maximum number of tones to be reproduced simultaneously, a key address code generator for successively producing key address codes corresponding to the respective keys, first detection means for examining whether there is coincidence of the key address code produced from said key address code generator with the key address code code already stored in said key address memory, second detection means for examining whether there is an unused channel in the channels of said key address code memory, a memory for storing the detection output of said second detection means, a logical circuit which, upOn receipt of the key data signal, produces a new key data signal when no key address code corresponding to the key data signal is stored in said key address code memory and produces a new key-on signal from said new key data signal only when there is an unused channel in the channels of said key address code memory, and gating means controlled by the new key-on-signal for causing the key address code from said key address code generator to be stored in the unused channel of said key address code memory

8. An electronic musical instrument as defined in claim 7 wherein said key assigner means further comprises a first delay circuit for delaying the key data signal from said key data signal generator for one said given key time period before it is applied to said logical circuit and a second delay circuit for delaying the key address code from said key address code generator for one said given key time period before it is applied to the gate of said key address code memory, said first detection means examining whether the same key address code as the one corresponding to said key data signal has already been stored in said key address code memory during the one key time period during which the key data signal is produced from said key data signal generator and said second detection means examining whether there is an unused channel during the next one key time period during which the delayed key data signal is applied to said key address code memory.

9. An electronic musical instrument as defined in claim 7 wherein said key assigner further comprises means for applying a key data signal indicating opening of the break contact to said logical circuit, means for producing a key-on signal upon receipt of the key data signal indicating closing of the make contact when the key address code corresponding to this key data signal is stored in said key address code memory by the key data signal indicating opening of the break contact, a key-on memory for storing this key-on signal and a logical circuit for producing a touch response signal having a duration which is equal to the interval between the opening of the break contact and the closing of the make contact in response to the outputs of said busy memory and said key-on memory.

10. An electronic musical instrument as defined in Claim 7 wherein said key assigner further comprises means for producing a key-off signal when the depressed key is released, a key-off memory for storing the key-off signal, means for detecting a state in which key address codes are stored in all of the channels of said key address code memory and producing an all-busy signal when said state is detected, means for producing, upon receipt of the key data signal relating to the make contact, a key-on signal when the key address code corresponding to this key data signal is stored in said key address code memory, a key-on memory for storing said key-on signal, a decay memory for storing a decay signal indicating a state of decay upon receipt of the key-off signal and an attack finish signal indicating completion of reading of an attack waveshape from an envelope counter which starts counting in response to the key-on signal from said key-on memory, means for detecting storage of the decay signal in any channel of said decay memory and producing an any decay signal when said storage is detected, a logical circuit for producing a truncate counter counting start signal which causes a truncate counter provided for said envelope counters to start counting upon receipt of the all-busy signal, the any decay signal and the new key data signal, means for storing a carry signal from said truncate counter indicating overflow of the computer and producing an any overflow signal upon detection of storage of the carry signal in any channel of said carry signal storing means and means for clearing contents stored in said channel of the key address code memory and the other said memories in response to said any overflow signal.

11. An electronic musical instrument as dEfined in claim 7 wherein said key assigner further comprises means for producing a pedal scanning signal when the key address code relates to the pedal keyboard and means for producing a pedal channel signal representing a specific channel assigned for the pedal keyboard, said key address code memory being caused to store the key address code relating to the pedal keyboard in said specific channel upon receipt of the pedal scanning signal and the pedal channel signal while storing key address codes relating to the manual keyboards in the channels other than said specific channel.

12. An electronic musical instrument as defined in claim 1 wherein each of said musical tone waveshape generator means comprises a frequency information memory which stores frequency data respectively corresponding to the notes of the keys and, upon receipt of the key address code corresponding to the depressed key from said key assigner means, produces frequency data corresponding to said key address code, counters which receive said frequency data and cumulatively count the same and musical tone waveshape memories which store musical tone waveshapes and have these waveshapes read out by the output of said counters.

13. An electronic musical instrument as defined in claim 12 wherein said frequency information memory comprises a read only memory having an access time of the order of 1 microsecond.

14. An electronic musical instrument as defined in claim 12 which further comprises at least one additional frequency information memory producing modified frequency data which is slightly different far each note from that of the first mentioned frequency information memory, counters provided for said additional frequency information memory for cumulatively counting the modified frequency data and musical tone waveshape memories which store musical tone waveshapes and have these waveshapes read out by the output of said counters, whereby at least two musical tones having frequencies which are slightly different from each other are simultaneously produced upon depression of a single key.

15. An electronic musical instrument as defined in claim 14 wherein said additional frequency information memory is an adder which adds together a digital data output from said first mentioned frequency information memory and information digital data obtained by shifting said first mentioned toward digital data output toward less significant digits thereof.

16. An electronic musical instrument as defined in claim 14 wherein said additional frequency information memory is an adder which adds together said frequency information and a digital signal representing a constant frequency value.

17. An electronic musical instrument as defined in claim 1 wherein said musical tone waveshape generator means comprises frequency information memories each being provided for respective keyboards and storing frequency information with respect to the corresponding keyboard which is approximately the same as the frequency information for the other keyboards for one and the same note, means for selectively operating these frequency information memories in accordance with the keyboard to which the depressed key belongs, counters provided on the output side of the respective frequency information memories and cumulatively counting the read out frequency information and musical tone waveshape memories storing musical tone waveshapes and have these waveshapes read out by the output of said counters, whereby musical tones having pitches which correspond to the respective keyboards and are slightly different from one another for said one and the same note are obtained.

18. An electronic musical instrument as defined in claim 12 wherein said frequency information memory comprises memory means for holding the key address code from said key address code memory in storage for a period of time which is at least one channel period longer than said given key time period, a read only memory having an access time greater than 1 microsecond for reading frequency information corresponding to the notes of the respective keys and producing, upon receipt of the key address code from said memory means, frequency information corresponding to said key address code, and means for obtaining and storing the frequency information from said read only memory at a time which is one key time after application of the key address code to said memory means and outputting this key address code one key time later.

19. An electronic musical instrument as defined in claim 12 wherein said musical tone waveshape generator means further comprises logical circuitry for preventing the first digit output among the outputs of said counters from being applied to said waveshape memory when an integer output of frequency information is produced from said frequency information memory, whereby the sampling frequency of said musical tone waveshape memory is reduced to 1/2 .

20. An electronic musical instrument as defined in claim 1 wherein each of said envelope waveshape generator means comprises an envelope counter for counting a predetermined clock pulse in response to a control signal fed from the key assigner and an envelope memory storing a predetermined envelope waveshape and having this envelope waveshape read out by the counting output from said envelope counter.

21. An electronic musical instrument as defined in claim 20 wherein said envelope counter comprises means which, upon receipt of a first control signal representing depression of a key from said key assinger, provides an attack clock pulse to said envelope counter until the count in said counter has reached a predetermined value and means which, upon receipt of a second control signal representing release of the key from said key assigner, provides a decay clock pulse to said counter until to said counter when the count in said counter has reached a final value, whereby an envelope waveshape which rises after lapse of a predetermined period of time from the time when the key is depressed, sustains a constant amplitude thereafter, and falls from the time when the key is released.

22. An electronic musical instrument as defined in claim 20 wherein said envelope memory stores a waveshape which rises instantaneously and decays gradually thereafter and said envelope counter successively counts the predetermined clock pulse upon receipt of said first control signal to read the waveshape from said envelope memory, the counting being stopped upon completion of the reading of said memory.

23. An electronic musical instrument as defined in claim 20 wherein said envelope memory stores a waveshape which rises instantaneously and decays gradually thereafter and said envelope counter means counts a first clock pulse upon receipt of a first control signal until a second control signal is applied thereto and counts, upon receipt of said second control signal, a second clock pulse having a higher frequency than said first clock pulse, whereby an envelope waveshape which rises abruptly upon depression of the key, decays gradually thereafter and falls sharply upon release of the key is obtained.

24. An electronic musical instrument as defined in claim 20 wherein said envelope counter means repeatedly counts a key clock pulse during application thereto of said first control signal in such a manner that it resumes counting from the beginning after it has counted the last count so as to repeatedly produce an envelope waveshape which rises instantaneously, then decays sharply and rises instantaneously again while the key is depressed.

25. An electronic musical instrument as defined in claim 20 wherein said envelope waveshape generator means further comprises a clock selector adapted to produce a plurality of clock pulses which have frequencies respectively corresponding to frequencies of signals selected for the respective keyboards and which are commonly used by to all of the channels, whereby a clock pulse at a frequency corresponding to the kind of keyboard is obtaineD.

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