US3855893A

US3855893A - Electronic organ employing multiple waveform tone generators and chiff generators

Info

Publication number: US3855893A
Application number: US00180563A
Authority: US
Inventors: W Chase
Original assignee: CHASE OF CALIFORNIA
Current assignee: CHASE OF CALIFORNIA
Priority date: 1971-09-15
Filing date: 1971-09-15
Publication date: 1974-12-24
Anticipated expiration: 1991-12-24

Abstract

A musical instrument of the electronic organ type having multiple frequency generators for driving a plurality of waveshaping circuits to produce the desired range or gamut of organ voices or tones. Also, there is provided control circuits which modify the signals from the tone wave-shaping circuits to provide speech transients or ''''chiff'''' sounds to enhance the realism of the organ tones produced. Selected circuit combinations for sharing both wave-shaping and chiff-generating circuit components to effect economies of construction, are also disclosed.

Description

Chase United States Patent 1 1 1451 Dec. 24, 1974 [541 ELECTRONIC ORGAN EMPLOYING 3,340,343 MULTPLE WAVEFORM TONE 1132322 311323 ""*E 1""" 43/98? amp e GENERATORS AND CHIEF GENERATORS 3,505,461 4/1970 Omura et a1 84/1 .01 [75] Inventor: Willis E. Chase, Los Angeles, Calif. 3, ll/l97l Woody 84/101 3,617,603 11/1971 Wayne et a1 84/].24 X Asslgneei Chase 01 Callfm'ma, L05 Angeles, 3,660,587 -5 1972 Martin; 84/1.24 x

, Ca1if. [22] Filed; 15 7 I PrimaryExaminer-Richard B. Wi1kinson Assistant ExaminerStan1ey J. Witkowski [21] Appl" N04 180,563 Attorney, Agent, or FirmRoger A. Marrs .[52] US. Cl...... 84/1.24, 84,/D1G. 5 [57] ABSTRACT [5 l 6 u A musical of the electronic rgan hav Fleld of Search 1.2 ing multiple frequency generators for driving a plural- 4 2 541-23 ity of wave-shaping circuits to producethe desired I range or gamut of organvoices or tones. Also, there is References Clied provided control circuits which modify the signals UNITED STATES PATENTS from the tone wave-shaping circuits to provide speech 2,486,208 10/1949 Rienstra 84/126 transients 0r Sounds to enhance, the realism of 2,907,244 1 0/1959 Schreiber.... the organ tones produced. Selected circuit combina- 2,989,886 6/1961 Markowitz.. tions for sharing both wave-shaping and chiff- 2,989,887 M i w generating circuit components to effect economies of 3,006,223 10/1961 whlte construction, arealso disclosed. 3,037,413 6/1962 Markow1tz.. 3,333,042 7/1967 Brombaugh 84/1'.13 6 Claims, 9 Drawing Figures 7 a 75? E I 1444/ 0/75? 5 Zara/max I v Swizwd 1 g? [mazes/ 7 Fame 44/0 SEVCW 7 755 GEM/7w; I 1(4 MVEFOAM 5' 4 I Z55 Comm 14411 1075? 1 To? 8 S $727143:

- $C7/0/1/,Z' f/ZTEP 41/0 fkwacwcv 7,7 (EM/m fmwss/aw $00,905 'T CbA/r/Pcu.

#1 SECf/OMZ f/lrse 44/0 7155 (ex/rem 0C su /2y I I 5475? 41/0 I K (5V- 725 @A/TGDC fl pz p se i6 A H475? 44/0 WSW/i fig g [XfiP-SS/OA/ '2' CbA/TFDL wAvEEORM 1 I ELECTRONIC ORGAN EMPLOYING MULTIPLE T E GENERATORS AND CHIFF GENERATORS BACKGROUND F THE INVENTION Heretofore, many schemes havev been proposed for the generation of musical tones by electronic means to simulate the desirable and familiar sounds of a pipe organ. Certain of these" prior devicesemploy circuits for generating complex waveforms which are rich in harmonics, and the signals thus produced are thereafter filtered to remove unwanted harmonics and thereby yield residual waveforms resembling the'intended tone pattern of a classical organ instrument. Other schemes of the prior art employ means for simultaneously generating a plurality of sine waves, or other simple waveforms which are selectively added to result in the synthesis of a complex waveform resembling the desired waveforrnr Perceptible richness isadded to the tones produced by an electronic organ when all of the audio harmonics of a classical organ tone are generated along witheach I fundamental note. Additionally, an important element in the electronic production of organ tones which are intended tofaithfully or realistically fsimulate classical organ tones are: the presence of speech. transients known as chiff sounds. The achievement of this element has heretofore been very difficult to obtain since speech transients with the desired recognizable pitch characteristics have necessitated both single and multi-, ple types of speech'transients. There, has beena wide disparity between the recognized ideal in the-synthesis of realistic organ tones, and practical, economicimplementation of an instrument intended-to produce such tones. An overriding constraint on "a practical instrument is that of economies dictated by a minimization of complexity. Wherever possible, components should be shared or serve multiple. purposes. Thesuccess of any giveninstrumentis largely a measure of the degree to'which this aspect of design has been carried out.

BRIEF SUMMARY OF THE P S N INVENTION can be providedwith its own amplifier and expression control. As part of the tone generators; a plurality of speech transient, or chiff circuits arefemployed which desirably modify the, attack envelope of each keyed note.

Novel means are employed to economize on, or otherwise conserve, the number of circuit components necessary to fully implement an electronic organ having given tonal resources, as compared-with systems of the prior art intended to accomplishgenerally similar results. c

- It is, therefore,- an object of the invention to provide an electronic organ whose individual notes are derived from multiple complex-waveform tone generators, the

outputs of which are modified so that the desired harmonics stay in the note to simulate conventional organ tones. I

Another object of theinventionis to provide a novel and improved electronic organ whose individual tone generating subsystems are selectively keyed into operation by selected key switches providing control for a plurality of different outputs of dissimilar harmonic structure. I

Another object ofthe invention is to provide a novel and improved electronic .organ havinga plurality of frequency sources for establishing the pitch of the several waveshaping tone generator circuits. v

Still another object of the invention is to provide a novel and improved electronic organ, whose individual notes have a chiff sound added to the attack envelope thereof. p I

Yet another object of the invention is to provide a novel and improved electronic organ, whose individual notes may be made to have a chiff sound added thereto by means of circuits which do not require additional key contacts, thereby simplifying the wiring thereof.

It is yet anotherobject of the inventionto provide in an electronicorgan, a novel and improved means for generating a single or a multiple type chiff sound.

Still another object of the invention is to provide a novel and improved electronic organ in which the operation of the several individual notes are under the control of a direct-current key control system.

With these and other objects in view, which will be made readily apparent to those versed in the art from the following detailed description of exemplary and preferred embodiments, and.as shown in the accompanying drawings, the invention will be seen to comprise a novel and improved electronic organ,.the elements, features of construction, and cooperative arrangement of the parts as more particularly recited and defined in the clairns appended hereto.

- :BRIEF DESC IPTION OF THE DRAWINGS FIG: I is a block diagram illustrating the overall a'r- FIG. 2 is a schematic circuit diagram of the wave-- shaping circuit used to provide diapason reed and other voices.

FIG. 3 is a schematic circuit diagram-of an alternate embodiment of the apparatus of FIG. 2.

' FIG. 4 is a schematic circuit diagram of yet another waveshaping circuit constructed in accordance with the invention.. FIG. 5 is aschematic circuit diagramv of a waveshaping circuit useful for simultaneously generating open-flute and string voices.

FIG. 6 is a schematic circuit diagram of an arrangement for coupling individual tone generators.

FIG. 7 is a schematic circuit diagram of the circuit for ment for simultaneously applying chiff sounds to a plu-' rality of notes.

, DESCRIPTION OF THE PREFERRED EMBODIMENTS There is shown in FIG. 1 a block diagram illustrating the arrangement of the major subsystems comprising an exemplary embodiment of the invention. The instrument is of the type in which pulse tones containing a large number of harmonics are generated and thereafter the pulse tones are modified to result in tones having the desired waveform characteristics. To facilitate the exposition of the invention, only those parts -tive tone coloration, the desired voices or tonal resources of the organ will determine which combinations of the several waveshaping circuits will be emboddeemed necessary to a clear understandingof the conspective sharps. These reference frequency signals from source 1 may have any desiredwaveshape depending on the type of frequency sourceused, and the desired results from the multiple complex-waveform tone generators. First frequency source 1 may be of masteroscillator and divider construction using any state of the art master oscillator and divider chain. First frequency source 1 may also be of any state of the art non-locked (independent) oscillator construction. Its primary function is to establish the frequencies and the invention is not limited as to the type of frequency source used. v i

c A second frequency source 2 (or. more frequency sources) may beused to enhance'the tonal resources of the instrument and this source (these sources) may be of either or of both types of construction as given previously for the'first frequency source. :The' subject invention is the multiple waveform tone generator 3'vvhich, in this example, is set up to supply seven differing waveforms from two sections. Each section receivesfone frequency from the frequency source per note Each section may receive. thesame frequency from thesame frequency source, close to the same frequency from two separate frequency sources, octavely related frequencies, or other harmonicly or nonharmonicly related frequencies from the same or separate frequency sources.

The tone waves generated by generator '3 correspond to tones or voices required in organ music and therefore require minimal filtering for finishing which function is provided by the several filters and tab controls 4-12. Waveforms obtained from Section I of the waveform generator 3 are at the same exact frequency as supplied by frequency source 1 at all times and waveforms-obtained from section II are at the same exact frequency as supplied by frequency source 2 at all ied into a given system. For example, filters 10-12 driven from Section II of generator 3 may. comprise waveshaping circuits such as shown in FIG. 2.

control units 13-15. The expression controls are selectively adjusted by the musician to provide the required output level from the tone production system. Loudspeakers 16-18 reproduce vthe audio signals from the respective amplifier systems. These loudspeakers (16-18) may be mounted in suitable tone cabinets of the type well-known'to those versed in the art, to provide the required baffling and other acoustical properties.

' Asis known to those versed in the art, organs are frequently provided with devices called couplers"..These devices comprise a system of switchingcircuits associated with the key switches, whereby each key may play not only its nominal pitch, but also other'pitch'es that are harmonically related tothe note (key) played. These additional pitches may be either higher, or lower in pitch, or both. In the ensuing description, couplers have been omitted in the interest of simplifying an understanding of the invention. It should be understood, however, that couplers may readily, be incorporated into the system disclosed in a manner which will be obvious to those skilled in the art. That is, a single contact per key switch for a unison pitch willpermit the use of waveform generator of thetype comprising section II of generator 3 of H611. In this instance, the waveform from the frequency (master) source is a-squarewave is tapered to yield the desired musical characteristics,-

as will be described in connection with FIG. 5.

which is supplied on line 21'. This master signal'or driving signal will be shaped in the circuit of FIG. 2 to yield a modified sawtooth waveform which can be varied from almost a pure sawtooth to a steep-frontpulse having a gradual trailing edge. The circuit can also yield, simultaneously, a substantially'.' rectangular output pulse. The output of the modified sawtooth waveform can be tapered, note-by-note, to give any desiredtaper when working into a frequency flat filter, or onehaving 6 db/octave slope, a [12 db/octave slope, orany other desired slope. The output of themodified sawtooth may be channeled into two or more filters, each havingany desired slope, and wherein each individual output The circuit of FIG. 2 comprises a diapason? generator as. an example-which is keyed by a method which will be explained hereinafter and which imparts an attack and release envelope to the output which is similar to .a pipe organ diapason voice.

The squarewave drive signal 21 is applied to the generator circuit via the coupling capacitor 22 and is differentiated into a series of pulses. The amplitude of the differentiated pulses presented to the base of transistor 25 via resistor 23 is controlled by the resistance divider network comprising resistors 23 and-24.

Transistor 25 is biased beyond cut-off, and the pulse amplitude at its base is not sufficient to cause the transister to conduct. Bias issupplied via resistor 24 from' terminal 32. A positive operating potential is supplied to the'collector of transistor 25 through resistor 33; capacitor 34 bypasses the collector to a low-impedance (current sensitive) preamp connected to collection bus 35. Transistor 25 collector-to-base capacitance is thus bypassed to ground. Resistor 40 comprises a lowimpedanceload resistor. When the key (27-) controlling the operation of the diapason generator is closed, the base to emitter bias applied to the transistor 25-is effectively reduced, allowing the peaks from the differentiated drive signal to turn the transistor 25 on. The

attack envelope characteristics are controlled by resistor 28 and capacitor 3'1. The momentary turn-on of transistor 25, caused by the drive signal peaks causes the collector todraw' a pulse of current, reducing the Vc-e to near zero and sends the energy stored in capacitor'3i4 into collection bus 35 which has a low impedance. This pulseof current stops suddenly the instant capacitor 34 is completely discharged, thus generating.

the desiredrectangular pulse on bus 35.

At the same time as the foregoing functions are occurring, the current in resistor 33 increases sharply as capacitor 34 is discharged. Then, when transistor 25 'cuts off again, the current in resistor 33reduces gradually until either capacitor 34 is completely recharged,

.or transistor 25 again draws a pulse of current. This sawtooth-like current variation appears-as'a signal on collection bus'36. The preferred sawtooth diapason toneis achieved when. transistor 25 conducts for roughly two to three times as longas it takes to com pletely discharge capacitor 34. This is onlya small percentage of the operating cycle. The balance of the op- ,erating cycle is spent in recharging capacitor 34.

pliedito collection bus 35. e i

When the, key 27 isopened, the negative cut-off bias Y from the terminal 32; is restored, causing transistor 21 to not respond to the incoming sync pulses on line rectangular output pulse is to be derived from the collector of the transistor instead of, or in'addition to, the outputcapacitor discharge pulse. This circuit comprises transistor 61 which receives an incoming sync pulse at its base 62 from an input network of the kind previously described in connection with the circuit of FIG. 2. The keying circu it is likewisethe same as that of FIG. 2. The output pulse-storage capacitor 63 looks into the network comprising resistor 64, diode 65, and resistor 66. Positive operating potential is supplied to :resistors 67 and 71 .via terminal 68. The modified sawtooth waveform appears on collection -bus 72 (leading to filter 74) and is isolated from collection bus 69 (leading to filter 73) by means of checking diode 65.

FIG. 5 illustrates a circuit arrangement for channelling the modified sawtooth waveforms (derived from circuits of the types shown in FIGS. 2- 4) into separate collection busses sothat they can be tapered individu ally, such as required'to produce open flute tones and for string tones. The number of outputs so tapered can i be greater than the two shown. The collector of transistor 81 supplies 'collectionbus 82 via resistor 83, and collection bus 84 via resistor 85. The rectangular output-pulse bus 86 derives its signal from storage capacitor 87. The low-impedance load comprises resistor 88. It is not required that more than one collection bus beconnected to the positive supply terminal 89.

The circuitsshown in FIGS. 4 and .5 may be combined to give a multiplicity of rectangular outputpulses .and modified sawtooth waveform outputs. u FIG. 6 illustrates the sharing of the keying control circuit with more than one diapason generator, allow-. ving moreefficient. generating of multiple pitches;-inter and intra manual coupling is also facilitated through the use of this circuit. The attack envelope of the diapason signal is controlled by resistor 91 and capacitor 92. The input drive signal from a first frequency source is applied to transistor 93 via series capacitor 94 and resistor 95. A. negative bias is supplied from terminal 96 s to the base of transistor 93'via resistor 97. Similarly, the

21. Releaseenvelope characteristics arecontrolled by supplied to a filter 39 corresponding to one'of the several filters 4-12 of the .apparatus'of FIG. 1.

Itshould be understood that a multiplicity of like circuits, of the type shown in FIG. 2, may be employed to produce all of the required diapason notes of the organ.

FIG. 3 illustrates a modificationof the circuit of FIG. 2 wherein a common-base connection to the transistor is employed (in lieu of the common-emitter connection of FIG. 2), as is especially useful where the input drive signalisjderived from'a low-impedance source. The

functional operation of the circuit of FIG. 3 is essentially the same as that previously described, and components 41-60 correspond, respectively, to components 21-40 of the first-described circuit. v

- FIG. 4 illustrates yet another modification of a waveform generator wherein the collector pulse of the transistor is isolated from thesawtooth waveform by means I drive signal from another frequency sourceis supplied to transistor 98 via capacitor 99 and resistor 101. Bias to transistor'98 is obtainedfrom terminal 96 via resistor 102. The release envelope is controlled by theseries combination of

resistors

103, and 97 in parallel with the series combination resistors 104,101 and l02,and capacitor 92. More than two'diapason generators can use the combination of resistor 91 and capacitor 92.

- The first output sawtooth is supplied to collection bus 117 sends the rectangular output pulse to bus 118, to

which isconnect ed load resistor 119. Filters l'13 and 121 are energized by busses and 114, respectively.

Each of the transistors shown in the previously discussed circuits-comprises an NPN type. It should be understood however that PNP transistors will work just as well providing that the DC operating voltage polarities are reversed, and the polarity of the sync signals are reversed. A chiff sound may be added to the generator of the type shown in FIG. 6 if the organ has a unit rank (such as flute) with chiff as is described in the following paragraph. l

In order to realistically simulate the sound of a conventional pipe organ, it is necessary to impart to a least some stops of the voiced notes a characteristic attack or speech transient called chiff. More particularly,

these transients normally occurduring .the initial speech period of a flue organ pipe. Thevpresence of such a sound results in clearly discern'able articulation of the speaking stop-Generally speaking, the principal I characteristic of such transients is the occurrence, for a fraction of a second at the onset of the note, a frequency or pitch which is different than that which is cases, a lower than normal pitch comprises the desired chiff sound; Chiff so'unds may be synthesized by mementarily .coupling an available signal fromanother tone generator to the keyed noteso as'to cause the couthe output. with circuit variations may be excessive. The circuit will operate, if transistor 123 does not cut-off, but the output amplitude variations. with changes in circuit component tolerance may be excessive.

The attack characteristics, exclusive of chiff are determined by thetime constants of resistor 132 and capacitor 133, and resistor 150 and capacitor 126, and their combination. Normally, resistor 131 will have a .value which is a small percentage of the resistance value of resistor 132. Chiff characteristics are determined by resistor 132, capacitor 133, and resistor 131 of the upper chiffed note in combination with resistor 129 and capacitor 126 in the upper chiffed note which control the attack envelope. The amount of chiff is readily'controlled by varying the resistance of resistor 131 on the chiffed note. If chiff isnot desired, return the end of capacitor 133 to ground as indicated in FIG. 7. The waveform appearingon collection bus 134 will be a squarewave with the positive-going portion being pled signal to speak for the brief interval at the onset v of the keyed note. The previouslydescribed generators of FIGS 2-6 required certain modifications to permit such transitory coupling. This'is done because the diapason generator does not have the added capacitor needed to control the'attack of the chiff while the generator described'below in connection with FIG. 7 does,

and can accept a chiff pulse from the diapason genera- FIG. 7. This point is'identifie'cl as point 122 in FIG. 7.

Note that the keying'voltage must be removed from the diapasong'enerator when the stop is not drawn to avoid the possibility of having a note -speaking.

The circuit of FIG. 7 is generally 'similarto' those de- "scribed previously inconne'ction with FIGS. 2-6, and

comprises a transistor 123 which receives a sync signal from its associated master oscillator via resistor 124.

I The multiple waveform generator of FIG. 7 operates in the following manner. The amplitude of the sync signal at the base of transistor 123 is controlled by the voltage-dividing

network comprising resistors

124 and 125. Capacitor 126 presents a very low impedance to this signal. The key 127 being open, the emitter-base junction of transistor 123 is biased sufiiciently negative by the resistor

combination including resistors

128, 129, 131, and 125, and the average potential supplied through resistor 124, that transistor 123 does not conduct. When the key 127 is closed, the bias applied to the emitter-base junction of transistor 123 from terminal 130 ischanged, allowing-transistor 123 to conduct on'the positive-going portions of the squarewave. Best operation is obtained if transistor 123 saturates on the positive-going portion of the squarewave, and cuts-off on the negative-going portion of the squarewave. The circuit will operate if transistor 123 does not saturate, and the output waveforms are usefuL-but changes in chiff sound audible with no somewhat rounded dueto the loading of the other two waveform subcircuits, If more rounding of the waveform is desired, which adds evenharmonics, capacitor .may be added. The waveform on collection bus 136 will be a pulse having a high harmonic content and consisting of one pulse from the differentiated squarewave following by-a much-truncated pulse of the opposite polarity. By adjusting the bias on the collection bus (obtained via resistor 137), the amount of truncation of the opposite polarity pulse is controlled from none, to nearly complete. This truncation is accomplished by diode 138. Note that diode 138 may be connected for either the positive going pulse, or the negative going pulse. If desired, diode 138 may be individually keyed. The modified squarewave that goes to collection bus 134 must be present when this is done for the note to sound. If maximum fwoodiness"- is desired in the tone available on collection bus 134, the polarity of diode 138 as shown in FIG. 7 is best. The waveform on collection bus 139 consists of a squarewave which appears on the negative-going half cycle, and a sawtooth (or modified sawtooth) which appears on the positive-goinghalf cycle. This is accomplished by transistor- 123 discharging capacitor 141 through diode 142 when transistor 123 saturates. When the transistor 1 23 cuts-off, capacitor 141, being decoupled by diode 142, recharges through resistor 143. The harmonic content is between the two above described waveforms. I

Thewaveform on collection bus 144, which is at low impedance (looking into load resistance 145) is a negative-going pulse related to the discharge current of capacitor 141. Its amplitude and pulse width are controlled by capacitor 141 and resistor 146. It has a sharp leading edge and a gradual decay of the trailing edge following by a very much reduced half-cycle of squarewave shape by virtue of the charging current entering capacitor 141 through resistor 143.

The waveform on collection bus 147, which is also at low impedance (looking into load resistance 148') is a negative-going pulse related to the discharge of capacitor 149-through diode 138 and is trapezoidal in shape. That is, it has a deep leading edge, a gradual decay of the trailing edge, followed by a sharp decay causing its tone to be different from the waveform on collection bus '144. This sharp decay is caused by diode 138 going out of conduction. Note that all five waveforms (appearing at 134, 136, 139, 144 and 147) may not be required from the generator, in a given application. If the v9 I waveformon Collection bus 134 is not required, the circuit remains the same (capacitor .135 may be omitted) and collection bus 134 is connected directly'to the supply voltage at terminal 151. If the waveform oncol- .to the 'pre-set reverb voltage (from line 159) where diode 156 couples, and the circuit sustains at a more gradual-rate from that point. On normal sustain, (no sustain), the sustain bus 157is grounded to 154' or bilection bus 144 and/or 147 is not required, then the 5 ased close to ground potential (either +or and the collection bus is tied to AC (or possibly DC) ground.

If the waveform on collection bus 136 and/or 139 is not required, then the collection bus is tied directly to its bias or supply 'voltage. If the waveforms on collection release envelope is snubbed to cut-off. The circuit of FIG. 8 further differs from that of FIG. 7 in the fact that the emitter of transistor 123" is the signal input point -(via resistor 124) instead of the base. The chiff operbusses 136 and 147 are not required, omitc'apacitor l ates in the same manner. as described previously, and

, 149, diode 138 and resistor 152. If the waveforms on collection, busses 139 and 144 are not required, omit capacitor141, diode 142, resistor 143 and resistor 146. If the waveforms on collection busses 139 and/or 144 142, 138 and resistors 152and' 153; Diode 142 is re- '1 placed by a solid connection, since its isolating function is not needed under this circumstance. If the waveform on collection busl31 is intended to generate a: flute tone, and no clarinettone is required,

a fuller tonecan be securedfor' certain types of flute tones (after filtering) by adjusting capacitor 135 for the desired amount, of harmonic distortionl. If the 'flute is tobe sustained for percussive effects, this 'IS desirable tion.'

is adjusted the same; it can also be omitted inthe same manner, as'previo'usl'y described. The addition of resistor 155, diode 1'56 and sustainfbus 157 and switch 158' circuits to'the'apparatus' of FIG. 7 as connected only, are required, omitcapacitors-149,- 135, diodes 15 to the key f end of" resistor 132 will equip the firstv described embodiment with variable-length sustain feature. It is realized that the circuits of FIGS. 7 and 8 contain one more resistor than isabsolutely needed if the operating voltages are specifically adjusted for the circuit, but the circuit shown conforms to a practical construc- As'was shown in the circuit of FIG. '6, two or more .multiplewaveform generators with chiff. can :be consince there'is some distortion on decay, and this can be nected to share resistor. 132. (or 132') and capacitor matched forsteady-state conditionsso that the tone decays with a minimum of harmonic change. An added advantage of using capacitor is that it increases the attenuation by by-passing the collector-to-base capacity of transistor 123 to ground. v

Another (though less satisfactory) method of distorting the modified squarewave on collection busil34 is Y to'partially bypass the baseof transistor 123 to ground 154 'so that the input squarewave is" rounded. This causes the cut-off time of transistor 123 to increase,

voicing. and mixing process.

FIG. 8 shows an alternate embodiment of the multiple waveform generator with chiff, in which a commonbase configuration is employed. This is especially suitable for use with J K flip flop drivers, while the previously described circuit of FIG. 7 is especially suitable for being driven by MOS-FET IC flip flops. The isolation of the keying and signal circuits makes for a more elegant long sustain effect, while the emitter degeneration reduces distortion on this'long sustain.

Those circuit components of the generator shown in FIG. 8, having functional counterparts in the generator of FIG. 7, are identified with like indicia except for the addition of a prime mark. For example, resistor 124 in FIG. 7 is the functional equivalentof resistor 124 in FIG. 8. Other components found in the circuit of FIG. r

8, not having: functional equivalents in the first-' described circuit, carry unique indicia.

155 and diode 156 will snub the release envelope down 133 (or 133") or one or more can share resistor 132 and capacitor 133 with one or more waveform generators whose equivalent is resistor 131 (or1131) and capacitorl4l (or. 141). Sustain times in these circuits 0 will be approximately equal. The chiff does not have to be limited to one note; twoor more notes may be chiffed to really put the Ch in the chiff. This isshown in the embodimentof FIG. 9 and is accomplished by feeding the chiff pulse to the desired notes, while isolating the notes with diodes. 1 Referring to the'c'ircuit of FIG."9, the sounding generator 'comprisesftransistor 16 1 vwl 1 ich receives it"s sync 'signal via reSistorlGZi'The output to the collection bus circuit is via resistor Chiff pulses from other notes 0 are applied via a matrix of diodes 164165 .to point 166. Resistors 167 170 functionally correspond-to

resistors

129, 131, 150, and 170, respectively, of FIG. 7.

' Capacitor 1'60 corresponds to capacit r 126 of no.7. v Resistorf140v corresponds to resistor 125. Thekeying 5 voltage is obtained via key 172. The chiff drive signal is obtai'nedvia capacitor 173 (which funetionally corresponds to capacitor 133 of FIG. 7). Resistor 174 is required to allow chargingand discharging of capacitor 173.

Thefirst chiff generator comprises transistor 175,

and the. second chiff generator comprises transistor 176. The remaining circuit components have identical functions to those previously. described having like indicia except for the {addition of primes and'double primes A As will be evident from the foregoing description, the present invention provides a relatively simple and inexpensive tone generating means having a high degree of flexibility and presenting a number of operating advantages. Any desired'note or notes can be coupled to obtain the desired transient speech effect. While there has been shown and described particular embodiments of the invention, it will be apparent to On long sustain," any key (e.g.,key 127) being closed 65 will raise the sustain bus 157 to the keying voltage potential. On short sustain, (or reverb" sustain), resistor those skilled in the art that numerous other modifications and variations may be made inthe form and construction thereof without departing from the disclosed fundamental principlesof the invention. It is therefore scope of the invention all such similar and modified forms of the apparatus disclosed, by which the results of the invention may be obtained by substantially the same or equivalent means.

What "is claimed is: 1. In an electronic musical instrument for obtaining complex waveforms comprising in combination:

afrequency source supplying pulses continuously at a given rate; 7 means for modifying the waveshapes of said pulses so that each waveshape thereof has a plurality-of selected harmonics; 7 1 i key switching means connected tosaid waveshape modifying means for selectively rendering said waveshape modifying means operative; filter means responsive to the output of said waveshape modifying means for adjusting the amplitudes of said harmonics to c onform to the timbre of a given musical tone; means responsive to said keyswitching meansfor imparting'a controlled change in selected harmonics of said waveshape modifying means for the purpose and signal translating means responsive to the output of saidfilter means to produce an audible musical tone. v

2. A waveshape generating circuit as defined in claim 1 wherein:

said continuously generated pulses comprise rectangular pulses and said waveshape modifying means comprises a rectangularto-sawtooth wave converter.

3. In an electronic musical'instrument for obtaining complex waveforms comprising in combination;

a frequency source supplying pulses continuously at a given rate;

means for modifying the waveshapes of said pulses so I that each waveshape thereof has a plurality of selected harmonics;

key switching means connected to said. waveshape modifying means for selectively rendering said waveshape modifying means operative;

filter means responsiveto the output of said waveshape modifying means for adjusting the ampli tudes of said harmonics to conform to the timbre of a given musical tone;-

means' responsive to said key switching means for imparting a controlled starting transient to the output of said filter means; v

signal translating means responsive to the output of said filter means to produce an audible musical tone; and

said continuously generated pulses comprise rectangular pulses and said waveshape generating means comprises a rectangular-to-sawtooth wave converter.

4. An electronic musical instrument comprising:

a plurality of continuously operated pulse signal sources providing individual driving signals at repetition rates corresponding to the semitone intervals of an octave of the tempered musical scale;

a plurality of waveshape modifying mean's'each of Y which is connected to acorresponding one of said pulse signal sources for producing acorresponding complex tone signal, having multiple harmonics, the pitchof which is that of a correspondingnote of the musical scale; V

a plurality of key switching means for selectively rendering corresponding ones of said waveshape modifying means operative;

a plurality of first filter means, each being connected to a corresponding one of said waveshape modifying means, for adjusting the amplitudes of the harmonics of said complex tone signals obtained therefrom to provide an output that conforms to the timbre of corresponding musical tones; a plurality of means responsive to actuation of a corresponding one of said key-switching means for I 5.-An electronic musical instrument as defined'in claim 4 including:

means for the summation of one or ing means for the purpose of strengthening or weakening certain harmonics of the resulting summation tone. signals to provide further enhancement of the tonal resources of the instrument. 6. An electronic musical instrument as defined in claim4including:

an impedance-changing network connected to the output of said waveshape modifying means for pro-' viding a second complex tone signal.

more of the complex tone signals from a given waveshape modify-

Claims

1. In an electronic musical instrument for obtaining complex waveforms comprising in combination: a frequency source supplying pulses continuously at a given rate; means for modifying the waveshapes of said pulses so that each waveshape thereof has a plurality of selected harmonics; key switching means connected to said waveshape modifying means for selectively rendering said waveshape modifying means operative; filter means responsive to the output of said waveshape modifying means for adjusting the amplitudes of said harmonics to conform to the timbre of a given musical tone; means responsive to said key switching means for imparting a controlled change in selected harmonics of said waveshape modifying means for the purpose of giving a starting transient to said musical tone; and signal translating means responsive to the output of said filter means to produce an audible musical tone.

2. A waveshape generating circuit as defined in claim 1 wherein: said continuously generated pulses comprise rectangular pulses and said waveshape modifying means comprises a rectangular-to-sawtooth wave converter.

3. In an electronic musical instrument for obtaining complex waveforms comprising in combination; a frequency source supplying pulses continuously at a given rate; means for modifying the waveshapes of said pulses so that each waveshape thereof has a plurality of selected harmonics; key switching means connected to said waveshape modifying means for selectively rendering said waveshape modifying means operative; filter means responsive to the output of said waveshape modifying means for adjusting the amplitudes of said harmonics to conform to the timbre of a given musical tone; means responsive to said key switching means for imparting a controlled starting transient to the output of said filter means; signal translating means responsive to the output of said filter means to produce an audible musical tone; and said continuously generated pulses comprise rectangular pulses and said waveshape generating means comprises a rectangular-to-sawtooth wave converter.

4. An electronic musical instrument comprising: a plurality of continuously operated pulse signal sources providing individual driving signals at repetition rates corresponding to the semitone intervals of an octave of the tempered musical scale; a plurality of waveshape modifying means each of which is connected to a corresponding one of said pulse signal sources for producing a corresponding complex tone signal, having multiple harmonics, the pitch of which is that of a corresponding note of the musical scale; a plurality of key switching means for selectively rendering corresponding ones of said waveshape modifying means operative; a plurality of first filter means, each being connected to a corresponding one of said waveshape modifying means, for adjusting the amplitudes of the harmonics of said complex tone signals obtained therefrom to provide an output that conforms to the timbre of corresponding musical tones; a plurality of means responsive to actuation of a corresponding one of said key switching means for coupling a portion of the output of one of said waveshape modifying means to an input of another of said waveshape modifying means which has been made operative, for a controlled transient interval, and thereby impart a chiff pulse to the starting envelope of the complex tone signal from said other waveshape modifying means; and signal translating means responsive to the combined output of said plurality of first filTer means for producing audible signals.

5. An electronic musical instrument as defined in claim 4 including: means for the summation of one or more of the complex tone signals from a given waveshape modifying means for the purpose of strengthening or weakening certain harmonics of the resulting summation tone signals to provide further enhancement of the tonal resources of the instrument.

6. An electronic musical instrument as defined in claim 4 including: an impedance-changing network connected to the output of said waveshape modifying means for providing a second complex tone signal.