US 3854365 A
In an electronic musical instrument, a tone generator circuit and/or a tone control circuit including tone keyer circuits, each or either one of said tone generator circuit and said tone control circuit comprises: pulse generators associated with key-actuated switches, respectively; waveform memorizing means having at least one row of voltage dividers of which the division ratios are preset in characteristics corresponding to either the tone waveforms, the tone envelopes or the depression speeds of the key operated by the player of the instrument; sequential memory read-out means connected to the respective voltage dividers; and pulse generators thereby providing an enabling signal sequentially to the individual dividers every time a pulse is inputted from the pulse generators to read-out the memorized waveform in the form of a modified audio signal at the output side of the circuit. The memorized waveforms can arbitrarily be sampled (scanned) out by using a sampling circuit in the read-out means, thereby providing variations in the modified audio signal. The tone control circuit enables the tone level control in conformity to the depression speed of the key and tone envelope control without the need to employ the conventional charge-discharge circuit requiring a relatively large capacitance capacitor, and makes it easy to carry out circuit integration.
Description (OCR text may contain errors)
United States Patent 1191 Tomisawa et a1.
[ ELECTRONIC MUSICAL INSTRUMENTS READING MEMORIZED WAVEFORMS FOR TONE GENERATION AND TONE CONTROL  Inventors: Norio Tomisawa; Takehisa Amano;
Yasuji Uchiyama; Takatoshi Okumura, all of Hamamatsu, Japan  Assignee: Nippon Gakki Seizo Kabushiki Kaisha, Shizuoka-ken, Japan  Filed: Apr. 4, 1973  Appl. No.: 347,725
 Foreign Application Priority Data 3,760,088 9/1973 Nakada 84/103 3,794,748 2/1974 Deutsch.... 84/124 3,809,786 5/1974 Deutsch 84/101 [5 7 ABSTRACT In an electronic musical instrument, a tone generator circuit and/or a tone control circuit including tone keyer circuits, each or either one of said tone generator circuit and said tone control circuit comprises:
July 31, 1971 Japan 46-57830 Pulse generamrs associated key-actuated July 31,1971 Japan 46-57831 swlFchesl respectively; waveferm memorizing meens Sept. 16, 1911 Japan 46-71245 PF row of voltage f of Whleh Sept. 22, 1971 Japan 46-73441 the dwslon are Preset m Charactensties corre' sponding to either the tone waveforms, the tone enve- 52 us. Cl. 84/101, 84/103, 84/124 lePes the depression Speeds ef e key Operated by 51 Int. Cl c1011 1/00, GlOh 5/06 the Player efthe mstrumem; sequenfilel memory ee  Field of Search 84/l.Ol-1.03, means connected to the respective Yoltege dwld- 84/113, L18, 122424 126, 128 DIG. ers; and pulse generators thereby provlding an en- 11, D1029 abling signal sequentlally to the lndlvldual dividers every time a pulse is inputted from the pulse genera-  References Cited tors to rjegadxut (title memlorizehd waveforn:l in the; form o amo lle au slgna att e output 51 e o t e clr- UNITED STAThS PATENTS cuit. The memorized waveforms can arbitrarily be 3,482,027 12/1969 Okamoto et a1. 84/].03 l d (Scanned) out by using a Sampling i i in 35l5'792 6/1970 the read-out means, thereby providing variations in the modifiedaudio signal. The tone control circuit en- 36l0805 10/197] ables the tone level control in conformity to the de- 3:6lO:806 10/197 pression speed of the key and tone envelope control 3,626,076 12/1971 without the need to employ the conventional charge- 3,636,231 1 1972 discharge circuit requiring a relatively large capaci- 3,646,242 2/1972 tance capacitor, and makes it easy to carry out circuit 3,707,594 12/1972 integration. 3,743,755 7/1973 3,755, 0 973 14 Claims, Drawing Figures E'lliz Ni 2 ,121:
l l i E l Q1 5,5: 1 1 i WNEFORM 5 .swl 1 ENVELOPE l MEMORY MEMORY I i (SW2 5 6b 111] 11-1 1 i TONE WAVEFORM 5533 ENVELO$E i SOURCE MEMORY GEN 9 MEMOR 1 l I I l I ll Sci 8 STAIN DF AY l SWI CH WAVEFORM 1056s ATE COUNTER cojnren l l2 10 a i Y KEYING PULSE GEN 11 PATENTE 3:2 1 H974 sum 02 0F 14 FIG. 2 NORMAL SHORT AT: @RAT:
FAs'T LONG e? i i L l 5 D r g ATTACK FIXED DECAY g ENVELOPE 7 vouAeE v MEMORY GEN ER A$ E 5 8 GATE i 80 ON OFF COUNT 225% '00 COUNTER DETEC O 5 BUILD-UP no FALL-DOWN i DETECTOR v DETECTOR 5 L-- L 1 i u .JFIG. 4(0) 5 Tout FIG. 4th) RI R2 R4 R5 R7 R8 I TR'JQ r4 4 J r-:1 TRB 0| O2 0304 O5 O6 O7 08 PULSE COUNTER PATENTEE, LEE 1 71974 FIG.
3( cI 3(d) SHEET 3 0F I4l ON OFF F FN i s L PATENTE 358 1 H974 sum as 0F 14 PATENIEL HEB I 7 I974 sum 09 0F 14 mm mmooowc OP PAH-INTEL SEE I 7 i974 FIG.
3,854,365 sum 11m 14 $322215 f wmzramso o 2 a 4 5 s 7 s 9W INN REPRODUCED l0 l5 WAVEFORM f 0123456789 I2lBI4 0 REPRODUCED I WAVEFORM 2f 024 m4 2468 uz fl' no l0 REPRQDUCED 0 F WAVEFORM 4f 046E J U PAH-INTEL 358 l 3.854.365
sum 120F14 FIG. I4 95 TONE 96 3 E? TONE GENWKEYER FIG. l7(0) v FIG. mb)
Rloz v Rm 05 R10: RIOS Mm R107 RIO8 M101 Q j mm m Mm PULSE COUNTER ,88
sum 13 or m CON TACT CONTACT KEY WITH lb KEY WITH lo ENVELOPE DEPRESSED 2 RELEASEDy) gTERMlNATlON SIGNAL CLOCK JIIHHI hnmum FIG. l5(o) IMI FIG. |5(b) FIG. 15m fi FIG. l5(d) imm- FIG. 15(e) FlG.:l5(j) 11mm FIG. 15(
FIG. I501) L DECODER OUTPUT O.l.2r----l5.l.2r
FIG. 15(9) 'fi FIG. l5(e)' l F FIG. l5(j) 4n -n BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention pertains to an electronic musical instrument provided with waveform memorizing means which is utilized in tone generating circuits and- ,/or tone modifying circuits including electronic keyers and keying circuits, and more particularly, it relates to a specific system for producing waveforms and having an aforesaid waveform memorizing means which is useful for the electronic musical instrument.
2. Description of the Prior Art In the conventional electronic musical instrument, a number of tone oscillators each having a different oscillation frequency are provided, whose output signals are synthesized in an appropriate manner to obtain a tone waveform. Such waveforms have been produced by another means, for example by passing a waveform containing a number of higher harmonics through filters of a complicated or sophisticated construction.
However, the conventional musical instrument which requires a number of tone oscillators or filters is too complicated to construct on a mass production basis and is difficult and troublesome to perform the adjustment of each oscillator and is not easy to obtain tone signals having desired complex waveforms. Thus, in the conventional instrument it has been hardly possible to produce natural sounds having complex and delicate waveforms resembling those produced by a natural musical instrument such as a guitar, piano and other instruments.
One conventional method for controlling or modifying the waveform of a keyed tone signal, that is, the prior method is to provide the so-called tonal envelope characteristics to the keyed tone signal which characteristics include a build-up portion made upon the depression of a corresponding tonal key, a sustain portion and a decay portion made upon the release of the depressed key. Thus the method comprises providing tone keyer circuits each having a charge-discharge circuit using a capacitor; applying a tone signal of a given amplitude to a corresponding one of the keyer circuits; and arranging an on-off switch provided in the chargedischarge circuit to coact with a key-operated switch. Thus, a tone signal with a predetermined envelope characteristic is obtained at the output side of the keyer circuits by the actuation of a single key. However, the charge-discharge circuit utilizing the capacitor cannot exhibit a complicated envelope characteristic which depicts a pattern consisting of an initially abrupt buildup curve with respect to the time axis, a steep descending curve at the extremity of the rise to a certain descending point and a subsequent slow decay curve, as is noted in conventional musical instruments. As a matter of fact, it has been considered in this field of art that any electronic musical instrument is acceptable for practical use only if it is provided with tone envelope characteristics substantially resembling those of the natural musical instruments even though the resulting envelope characteristics are somewhat monotonous and not sufficiently delicate.
As the tone control signal producing means for use in electronic musical instruments for producing a tone control signal in accordance with the depression speed of a playing key, there have been developed two kinds of so-called touch-responsive effect producing devices,
'the resistor and the capacitance of the capacitor, and
therefore the touch-responsive effect depends upon only the decay characteristic of the time constant, but
' this device is not always suitable for producing such tone signals as resembling those of the natural musical instruments at the output side of keyer circuits. Furthermore, the capacitor is required to be of a relatively large capacity in order to obtain a desired tone control signal responsive to the depression speed of the playing key, and so it has been difficult to make the tone control cirucit of the instrument in the form of an integrated circuit. Because of the substantial time lag in the response between the changing-over action of a keyoperated switch actuating the charge discharge circuit and the resulting constitution of a discharge path, a maximum voltage stored on the charged capacitor cannot be derived at the output side of the tone control signal producing circuit, so that upon the maximum depression speed of the playing key, the utilization factor of the charged voltage to the tone control signal is low.
On the other hand, the aforesaid induced electromotive force type device is such that the movable magnet and the coil are arranged so that interlinked magnetic fluxes generated in the coil can vary depending on the depression speed of the playing key or the electromotive force or the voltage resulting from the interaction of the coil and the moving magnet is charged to a Ca pacitor, thus utilizing a transient voltage variation across the capacitor during charging or a discharge characteristic of charged voltage through another discharge path. Thus, the touch-responsive effect may be said to be decided only by the factors of the coil and movable manget which are employed. This causes the same problems as mentioned above with respect to the case of the charge-discharge function type. In addition, the use of coils for generating an electromotive force makes the circuit integration of tone control circuits considerably inconvenient.
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electronic musical instrument of a novel type in which memorized waveforms are utilized to generate desired tone signals and/or to perform tone modifications for providing desired envelope characteristics of a keyed tone signal or for providing keytouch-responsive level control effects thereto, whereby producing musical tones resembling those of natural musical instruments with high fidelity, which eliminates the above-mentioned drawbacks of the conventional electronic musical instruments.
Another object of the present invention is to provide an electronic musical instrument comprising waveform memorizing means for memorizing various kinds of tone waveforms, a key-actuated clock oscillator acting as tone sources and waveform read-out means for deriving a tone signal having a given waveform from the memorizing means in accordance with a corresponding oscillating frequency of the actuated clock oscillator in which a tone signal with a memorized waveform as derived is amplified electronically to feed a loud speaker, thus not requiring a number of tone oscillators as well as a number of filters for processing tone signals of desired complex waveforms.
A further object of the present invention is to provide an electronic musical instrument comprising tone envelope waveform memorizing means in its tone gate circuit, namely, in its tone keyer circuit, said means including an attack envelope memory memorizing a build-up portion of the envelope waveform and a decay envelope memory memorizing a down-slope portion of the envelope waveform and envelope waveform readout means for detecting the depression and release of a key to thereby derive a corresponding envelope waveform from the memorizing means, which makes it possible to obtain a tone signal having a complicated envelope waveform resembling those of natural musical instruments by a simple construction and to adjust time intervals of the buildup portion and the downslope portion of the envelope waveform as desired.
A still further object of the present invention is to provide a specific wavefomi producing device having waveform memory therein, which is useful particularly for electronic musical instruments, in which the interlacing rate of a memorized waveform, i.e., the sampling frequency thereof is variable with an increase in frequency of the narrow band basic signals, whereby producing required wide band frequency signals without actively raising a quantized noise frequency.
A further object of the present invention is to provide an electronic musical instrument provided with tone control signal producing means including a waveform memory for memorizing amplitude variations with respect to time or depression speeds of a key, and arranged to be operative so that, upon depression of a specific key, a tone control signal corresponding to its depression speed is read-out for controlling the amplitude, frequency, tone color and phase of a tone signal, whereby a touch-responsive tone control signal is obtained.
Yet a further object of the present invention is to provide a novel construction of a tone generator and/or a large number of tone control circuits, which is suitable and convenient for circuit integration, and is easy to manufacture on a mass-production basis and is not expensive, and does not require a large capacity capacitor and a coil.
Another object of the present invention is to provide an electronic musical instrument which has a solidstate circuit arrangement in its sound production system such as a tone generator and tone keyers and a power amplifier including a tone processing waveform memory.
In accordance with the present invention, there is provided a waveform producing system comprising: a waveform memory having resistive voltage divider networks for memorizing a waveform in such a manner that the waveform is divided into a plurality of amplitude elements with respect to time and each amplitude is set to correspond to the division ratio of each divider;
a read-out means including a plurality of frequency divider circuits which are so arranged to be interchangeably cascaded for producing sampling pulses and for providing the pulses to said memory to sample (scan) the memorized waveform; clock signal generator means adapted to generate clock signals to drive the frequency divider circuits; and frequency divider connection change-over means disposed between said clock signal generator means and said read-out means to variably control the cascaded connections of the frequency divider circuits in accordance with the clock frequency of the clock signal delivered from the generator means so that the sampling number for the memorized waveform is reduced with an increase in the frequency of the applied clock signal to maintain the sampling frequency substantially constant.
These as well as other objects, features and advantages of the present invention will be well understood from the following detailed description made in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic block diagram of an embodiment of an electronic musical instrument in accordance with the present invention.
FIG. 2 is a schematic block diagram illustrating details of the tone envelope read-out means shown in FIG. 1.
FIGS. 3(a)( are diagrams illustrating waveforms associated with the blocks shown in the FIG. 2.
FIG. 4a is a circuit diagram illustrating an example of each waveform memorizing means as shown in FIG. 2, which constitutes the construction of an essential portion of the present invention, whereas FIG. 4b is a view showing a waveform memorized in the memorizing means of FIG. 4a.
FIG. 5 is a schematic constructional view illustrating an example of a semiconductor integrated circuit fon'ning the circuit arrangement shown in FIG. 4a.
FIG. 6 is an equivalent circuit diagram of a waveform read-out means or a pulse counter shown in FIG. 4a.
FIG. 7 is a graph showing waveforms at each portion as shown in FIG. 6.
FIG. 8a is a schematic block diagram illustrating a waveform producing system applied to an electronic musical instrument which is similar to the embodiment of FIG. 1, whereas FIGS. 8b-8d show graphs for explaining the operation of the system shown in FIG. 8a, respectively.
FIG. 9a is a schematic circuit diagram illustrating another embodiment of waveform producing system which is much improved from that of FIG. 9a, while FIGS. 9b-9d are graphs for explaining the operation of the system of FIG. 9a.
FIG. 10 is a functional block diagram illustrating the essential portion of the system of FIG. 9a in more detail.
FIG. 11 is a circuit diagram illustrating an example of an essential part of FIG. 10 in detail.
FIGS. l2a-l2d are diagrams for explaining the operation of the system shown in FIG. 9a.
FIGS. l3a-l3d are waveforms for explaining the output signal obtained from the waveform producing system of FIG. 9a.
FIG. 14 is a schematic circuit block diagram illustrating a further embodiment of the present invention which is so constructed as to provide a touchresponsive effectto the electronic musicalinstruments.
FIG. 15 shows various pulse waveforms developed at each portion of the circuit arrangement shown in FIG. 14.
FIG. 16 is a schematic block diagram illustrating a modification of the electronic musical instrument of FIG. 1 to which the circuit arrangement shown in FIG. 14 is applied.
FIG. 17a is a view illustrating an example of a waveform memorizing means used in FIG. 14, whereas FIG. 17b is a waveform obtained from the output of FIG. 17a.
It should be understood that like reference numerals and symbols indicate like parts throughout the drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, there is schematically illustrated an embodiment of an electronic musical instrument in accordance with the present invention, in which numeral 1 denotes a keyboard, 2 a key switch circuit section, 3 a tone source circuit section, 4 a pulse counter, 5a-5d tone waveform memories, 6a and 6b tone envelope waveform memories, 7 a fixed voltage generator, 8 a sustain gate, 9 an attack counter, 10 a decay counter, 11 a keying pulse generating circuit, 12 an audio amplifier, 13 a loudspeaker, TA,TA., tone color tablets, AT, an attack control knob, AT a decay control knob, EP an expression pedal, SW,-SW, tabletactuated switches, SW SW an attack knob-actuated switch and a decay knob-actuated switch, respectively, and 9a and 10a an attack knob-operated pulse generator for the attack counter and a decay knob-operated pulse generator for the decay counter, respectively.
Envelope waveform memories 6a and 6b are provided to memorize an attack portion and a decay portion of a tone envelope waveform characteristic, respectively, while the fixed voltage generator 7 is provided to generate a constant voltage which works as a flat sustain portion of the envelope characteristic. These memories 6a and 6b are so constructed to deliver a memorized envelope waveform signal to a tone signal control side upon receipt of pulse signals from the attack counter 9 and the decay counter 10. The envelope waveform memories 6a and 6b are selectively operated by a selective operation of the envelope tablets ETA, and ETA, thereby to close either one of the switches SW and SW,,. Only for the convenience of explanation, description will be made hereunder of the case of operating the attack envelope memory 6a.
The keying pulse generating circuit 11 functions to control each of the attack counter 9 and decay counter 10 and the sustain gate 8 by the receipt of a keying pulse signal. That is to say, the circuit 11 makes the attack counter 9 operative to read-out attack envelope waveform memorized in the memory 6a upon a keyoperated switch being in its on state, and turns on the sustain gate 8 upon completion of counting by the counter 9 to develop a constant DC voltage from the fixed voltage generator 7 and then makes the decay counter 10 operative to read-out a decay envelope waveform memorized in the memory 6b when an off action of the key-operated switch is detected. Thus, a voltage representing the memorized envelope waveform is delivered to a line L, and is applied to the tone waveform memories 50 5d from the envelope memories 6a and 6b and the fixed voltage generator 7. Each of the tone waveform memories Sa-Sb has a tone waveform memorizing function and is of a substantially like construction as that of each envelope memory.
The tone source circuit section 3 is provided with oscillators associated with key-actuated contact switches of the key switch circuit section 2, each of which is capable of producing n'f clock pulses per second when a corresponding contact switch of the key switch circuit section 2 is closed by the depression of a corresponding key of the keyboard 1, wherein n represents an integer which corresponds to a sampling number of the waveform memory, and f represents a number corresponding to the frequency of a required tone pitch, which is variable with each key. Theproduced clock pulses are delivered to an n-stage pulse counter 4, so that this counter 4 recirculates f times per second to thereby produce output pulses at its output side. These output pulses are then applied to the tone waveform memories Sa-Sd which each memorizes a preset tone waveform to read-out the memorized tone signal waveforms. By a selective operation of tone color tablets TA,-TA., any of the switches SW,-SW., is interlockingly closed so as to select a required tone color or colors, and the thus derived tone signals are delivered from the tone waveform memories to the audio amplifier 12.
Now, let us assume that one switch SW, is closed. Whereupon, tone signals are successively read out from the corresponding waveform memory 5a, and they are subjected to tone envelope control by a tone envelope signal through the line L,, and then are amplified by the audio amplifier l2 and reproduced by the loudspeaker 13.
Alternatively, it will be understood that those readout tone signals derived from the tone waveform memories Sa-Sd may be keyed by using the conventional tone keyer circuit so as to provide a tone envelope effect, as another aspect of the present invention.
Referring to FIG. 2, there is shown a detailed block circuit diagram of an envelope memory 6a and keying pulse generating circuit 11 as shown in FIG. I, in which the memory 6a is indicated to include an attack envelope memory 6a and a decay envelope memory 6a,, and the pulse generating circuit 1 l is indicated to have a build-up pulse detector 11a and a falling pulse detector 11b. I
Description will hereunder be made of the operation for obtaining an envelope control signal voltage by the arrangement of FIG. 2 with reference to the graphs of FIG. 3 which depict various waveforms at each part of this arrangement.
When a keying pulse signal having a waveform of FIG. 3(a) is applied to the keying pulse generating circuit 11, a build-up pulse as shown in FIG. 3(b) is produced by the build-up signal detector Illa, and is applied to the attack counter 9 to initiate the operation of the counter. An output pulse derived from the counter 9 is applied to the attack envelope memory 6a,, thereby reading out or deriving a voltage of the memorized attack envelope from the memory 6a,. At the termination of counting of the attack counter 9, a pulse which is representative of the termination of counting is generated by a count termination detector 8a, which pulse has a waveform as shown in FIG. 3(d), and turns the sustain gate on" to thereby develop a DC voltage of a constant amplitude as shown in FIG.
3(e) in the fixed voltage generating circuit 7. Subsequently, when the key-operated switch is turned of a falling (negative going) pulse as shown in FIG. 3(e) is produced by the falling pulse detector 11b. The falling pulse causes the sustain gate 8 to be turned off, thus stopping the generation of the fixed amplitude voltage at the generator 7, and simultaneously it is applied to the decay counter to thereby initiate the operation thereof. Thus, count signals from the decay counter 10 are applied to the decay envelope memory 6a, for reading the memory, so that a voltage representing a memorized decay envelope waveform as shown in FIG. 3(i) is read out at the memory 6a Therefore, it will be seen that, by'the depression and release action of the key, an envelope representing a voltage having the entire rise and fall waveform shown in FIG. 3(j) is produced serially with respect to a time interval between 1, and t,.
It should be noted that the operation interval of the attack counter is variable through the range of from fast point F to normal point N as shown in FIG. 3(f) as required by changing the oscillation frequency of a clock oscillator 9a for driving the attack counter, while the operation interval of the decay counter is also variable through the range between short point S and long point L as shown in FIG. 3(g) as required by varying the oscillation frequency of another clock oscillator 10a for driving the decay counter.
FIG. 4(a illustrates the detail of each of the abovementioned waveform memories. By way of example, a circuit arrangement applied to either one of the tone waveform memories 5a-5d is described hereunder. However, such an arrangement is, of course, applicable to the above-mentioned attack envelope memory or decay envelope memory in a similar manner as in the case of each tone waveform memory, though not described in detail. R, through R, denote resistors, the resistances of which are set to be in correspondence with sampled (scanned) amplitudes of the waveform to be memorized. In this drawing, each resistance value is indicated by the length of the resistor simply for the purpose of illustration only. One ends of the respective resistors R, to R are connected to a common line which in turn is connected through a load resistor R to a terminal T to which a power voltage is applied. The connection point Tout between the load resistor R and the common line constitutes an output terminal. Though an envelope control voltage derived from the envelope waveform memories is applied to the terminal Tout as will be seen from FIGS. 1 and 2, it is assumed hereinafter that a constant amplitude voltage as the envelope control voltage is imparted to the terminal merely for the simplicity of explanation. The other ends of the resistors R, to R are connected to switching elements such as field-effect transistors TR, through TR,, at their drain electrodes, respectively, the source electrodes S of which are commonly grounded and the respective gates G of which are connected respectively to output terminals 0,, O 0,, of the pulse counter 4. In the waveform memory arrangement, when a predetermined number of clock pulses as a source signal are applied to an input terminal T, of the counter 4 from the tone source circuit section 3, a pulse voltage is developed at the terminals 0,, O 0,, sequentially and thus is shifted at these output terminals in recirculation. Accordingly, if a pulse voltage is present at the terminal 0, and is applied to the gate of the transistor TR,, the
latter is rendered conductive, so that a current flows through a path composed of: terminal T, load resistor R, resistor R,, the drain and the source electrodes of the transistor TR, and ground, thus deriving a DC voltage in value corresponding to the resistance of the resistor R, at the output terminal Tout; that is to say, reading out a part of a waveform memorized in the form of resistance at that terminal. When the pulse voltage is present successively at the terminals 0 O O and when these voltages are applied to the respective gates of transistors TR,, TR,,, TR,,, voltages representative of the corresponding resistors R R R are developed at the output terminal Tout successively in a similar way as that described previously. These voltages appearing at the output terminal Tout are indicated with respect to time as a waveform shown in FIG. 4(b From this fact it will be apparent that a tone signal waveform as required can be made to appear at the output terminal Tout by appropriately setting the resistance value of each resistor as memorizing element.
FIG. 5 illustrates schematically a plan view of an integrated circuit of the waveform memory shown in FIG. 4, in which example, let us assume that an MOS (metal-oxide-semiconductor) is used as the integrated circuit, and also that p-channel field-effect transistors are used as transistors for the convenience of explanation. In this drawing, DL represents p-type diffused layers, GE gate electrodes of MOS transistors, MD metaldeposited regions, and CP connections between the metal deposition regions and the p-type diffused layer. In a semiconductor substrate, a plurality of p-type diffused regions P,, P P are buried, and they form resistors of strip shape. Each resistive strip is interconnected with an aluminum-deposited layer at such a position as will constitute a resistance corresponding to an analog quantity of a waveform to be memorized. Namely, the lengths e,, e e,, of the p-type diffused regions P,, P P are set to be in correspondence with the sampled (scanned) amplitudes of an analog waveform, and hence these diffused regions have resistance values in accordance with the lengths thereof, respectively, of which the lower ends are connected to the drain regions of the MOS p-channel field-effect transistors TR,, TR TR,,, respectively. Transistors TR, to TR,, are so constructed as to be rendered conductive by receiving a pulse (negative) voltage being applied to each gate thereof from the pulse counter 4. Accordingly, if a negative going pulse which has a sufficient magnitude to render the transistors TR,, TR,, TR,, conductive is applied to the gate electrodes thereof from the counter 4 successively, these transistors are also rendered conductive only during the period in which the successive pulses are supplied to each ate, renderin these transistors on-off" successive] r g g The common connection line of the aluminumdeposited layer with the resistor, array is connected through the load resistor R having a suitable resistance value to a negative power source, though not shown, and hence, output voltages corresponding to the lengths 1,, l 1,, of the p-type diffused regions P,, P P are successively derived or read out at the terminal Tout of the aluminumdeposited layer Al. It will be seen that the lengths 1,, l 1,, of the regions P,, P P correspond to the resistors R,, R R, as shown in FIG. 4(a). In FIG. 5, the pulse counter 4 is indicated as a structure of an integrated circuit. The p-type diffused resistive layers are used as source electrodes and drain electrodes of MOS field-effect transistors and as interconnections.
The equivalent circuit of the pulse counter 4 in FIG. is as shown in FIG. 6, which circuit has three cascaded flip-flops FF F F and FF The first flip-flop FF 1 is provided with the input terminal T to which a series of clock pulses are applied from the tone source circuit section 3. Consequently, the respective outputs X, Y and Z of the flip-flops FF FF and F F present waveforms as shown in FIG. 7. M M M denote pchannel MOS field-effect transistors which function to produce inverted outputs X, Y and Z from the outputs X, Y and Z of the flip-flops, and M8,, M5 M8,, (for example MS denote MOS field-effect transistors which function to produce an output signal for driving the gate electrodes of transistors TR TR TR in accordance with these signals X, Y and Z and X, Y and Z. Transistors MS through MS are constructed so that a multiplicity of parallelly arranged p-type diffused layers Q,, Q Q and S S S may be disposed in interleaved comb-shape to one another and adjacent layers Q1 and 8,, Q2 and S Q8 and S are combined, respectively. Between each adjacent layers a thin oxide film is formed though not shown, and an aluminum film is deposited thereon so that layers 0,, Q Q serve as the drain portion and layers S S S as the source portion and the aluminum film as the gate portion.
Referring to the circuit of FIG. 6, transistors MS, through MS. constitute a logical NOR circuit N wherein when its input signals X, Y and Z are concurrently zero, 1 signal having a negative voltage appears at the terminal 0 To the other terminals 0 to 0 similar NOR circuits N to N, are connected. The following table shows the relationship between the inputs for NOR circuits and the count outputs appearing at terminals 0 to 0 Table INPUT x x x x x x x x Y Y Y Y Y Y Y Y INPUT TERMINAL 2 z z z z z z 2 o 1 o o o 0 0 o o 0 o l o 0 o o o o 0, 0 0 l 0 0 0 0 0 0 0 0 0 1 o 0 o 0 0, 0 0 0 o l 0 0 0 o, 0 0 o 0 o 1 0 o 0 0 o 0 0 o o l 0 o, o 0 0 0 0 0 o I As will be understood clearly from the foregoing statement, it is recognized that, when pulses are applied successively to the counter 4, count output signals are derived sequentially from the terminals 0 to O Though the pulse counter 4 has been described with respect to a specific embodiment, counters of any other type may be used provided that they have such a function that output pulses are produced in succession at successive output terminals in accordance with the inputting of pulses. Through FIGS. 4-7, there has been described an embodiment of a tone wavefomi memory and a counter for driving the memory to read out or extract the memorized waveform. However, the combinationof the attack envelope waveform memory with its attack counter, or the combination of the decay envelope memory with its decay counter can be manufactured in a similar construction to that of the preceding embodiments.
Thus, the electronic musical instrument which employs various waveform memories as tone generators and tone envelope effect producing means as mentioned above is quite advantageous in that it is capable of producing tone signals each having a desired complicated and delicate waveform with tone envelope effects which really resembles that of a natural musical instrument, and in that the instrument makes it possible to artbitrarily adjust, in a simple manner, the time interval of the build-up portion or the decay portion of the tone envelope.
Now, an analytic discussion will be made of a waveform producing apparatus utilizing a waveform shaping technology using memories, which can appropriately be applied to accomplish the purposes of electronic musical instruments. First, the tone signal generators of the preceding embodiment are illustrated as a waveform producing apparatus as shown in FIG. 8(a). The tone source circuit section 3 has a plurality of clock pulse oscillators, each of which is capable of generating n.f clock pulses per second when a corresponding key of keyboard 1 is depressed so that a corresponding one of the key-actuated switches 2 is closed to a conducting position wherein n represents an integer which corresponds to the sampling number of a waveform memorized into waveform memories 5, while f represents a fundamental frequency of a required tone pitch corresponding to the keys name. The clock pulses thus generated are delivered to a frequency divider circuit which comprises cascaded flip-flops and then they are delivered to a decoder at n-input terminals at which are sequentially developed pulse signals. Thus, the frequency divider circuit and the decoder, in combination, constitute an n-stage successive pulse generator 4, which therefore, recirculates f times every second to produce pulses at its output side. Each of the waveform memories 5 comprises a bank of parallel-connected resistors with individual serial-connected electronic switching elements, each resistor being adapted to be connected with a common load resistor to constitute a voltage divider circuit in cooperation with the switching element, the dividing ratio of which is set so as to correspond to one sampling element of a waveform which is to be memorized into the memory with respect to a time axis. The voltage divider circuit is constructed so as to be operative so that, by receivinga pulse at the switching element, the switching element is rendered to the conducting state, and that as a result, the sampling element is derived in the form of a divided voltage at the output terminal of the memory. As has been described in the preceding embodiment, the waveform producing apparatus of this type has a number of advantages for example, realistic tone signals can be provided easily without requiring a multiplicity of tone os-