05/180563

12/24/1974

09/15/1971

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Chase, Of California (Los Angeles, CA)

84/699

84/710, 984/328, 84/DIG.005

G10H1/14; G10H1/06; G10H5/02; G10H1/02

84/1.01,1.11,1.19,1.22,1.13,1.24,1.26,DIG.5,1.23

3037413	Electronic organ with transient speech effects	June 1962	Markowitz
3333042	Electronic organ with chiff	July 1967	Brombaugh
3340343	Stringless guitar-like electronic musical instrument	September 1967	Woll
3445578	CHIFF AND TONE GENERATOR	May 1969	Cunningham
3476863	CONVERSION OF TONAL CHARACTER OF AURAL SIGNALS	November 1969	Campbell
3505461	ELECTRONIC MUSICAL INSTRUMENT FOR PRODUCING NOVEL ACOUSTIC EFFECTS FROM MULTITONE SIGNALS	April 1970	Omura et al.
3617598	SAWTOOTH TONE GENERATING AND KEYING CIRCUIT FOR AN ELECTRONIC MUSICAL INSTRUMENT	November 1971	Woody
3617603	CHIFF CIRCUITS FOR ELECTRONIC ORGANS	November 1971	Wayne et al.
3660587	ELECTRONIC ORGAN KEYING CIRCUITS	May 1972	Martin

Wilkinson, Richard B.

Witkowski, Stanley J.

Marrs, Roger A.

What is claimed is

1. In an electronic musical instrument for obtaining complex waveforms comprising in combination:

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

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

4. An electronic musical instrument comprising:

5. An electronic musical instrument as defined in claim 4 including:

6. An electronic musical instrument as defined in claim 4 including:

BACKGROUND OF THE INVENTION

Heretofore, many schemes have 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 devices employ 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 waveform.

Perceptible richness is added to the tones produced by an electronic organ when all of the audio harmonics of a classical organ tone are generated along with each fundamental note. Additionally, an important element in the electronic production of organ tones which are intended to faithfully or realistically simulate 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 multiple types of speech transients. There has been a wide disparity between the recognized ideal in the synthesis of realistic organ tones, and practical, economic implementation of an instrument intended to produce such tones. An overriding constraint on a practical instrument is that of economics dictated by a minimization of complexity. Wherever possible, components should be shared or serve multiple purposes. The success of any given instrument is largely a measure of the degree to which this aspect of design has been carried out.

BRIEF SUMMARY OF THE PRESENT INVENTION

There is provided by the present invention a novel and improved electronic organ employing a plurality of independent tone generators, each of which produces complex signals having waveforms corresponding to conventional organ tones. The several tone generators are driven by frequency sources to establish the desired pitches, and are individually keyed and have their several outputs directed to corresponding ones of a number of separate output channels. Each output channel can be provided with its own amplifier and expression control. As part of the tone generators, a plurality of speech transient, or chiff circuits are employed 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 accomplish generally similar results.

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.

Another object of the invention is 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.

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

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.

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 another object of the invention to provide in an electronic organ, 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 claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the overall arrangement of the subsystems comprising an electronic organ constructed in accordance with the invention.

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 wave-shaping circuit constructed in accordance with the invention.

FIG. 5 is a schematic circuit diagram of a wave-shaping 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 providing "chiff" sounds to the attack portion of a note.

FIG. 8 is a schematic circuit diagram of an alternate embodiment of the apparatus of FIG. 7.

FIG. 9 is a schematic circuit diagram of an arrangement for simultaneously applying chiff sounds to a plurality 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 deemed necessary to a clear understanding of the construction and operation thereof are shown in the drawings. Circuits typical of the plurality of like circuits needed for all the notes of a practical organ are shown in detail wherever appropriate, it being understood that such circuits are repeated or replicated to the extend necessary for a full complement of notes.

Referring to FIG. 1, a first frequency source 1 produces a first set of primary or master signals which generate all the A, B, C, D, E, F, and G notes and their respective sharps. These reference frequency signals from source 1 may have any desired waveshape depending on the type of frequency source used, and the desired results from the multiple complex-waveform tone generators. First frequency source 1 may be of master oscillator 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.

A second frequency source 2 (or more frequency sources) may be used 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 which, in this example, is set up to supply seven differing waveforms from two sections. Each section receives one frequency from the frequency source per note. Each section may receive the same frequency from the same frequency source, close to the same frequency from two separate frequency sources, octavely related frequencies, or other harmonicly or non-harmonicly 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 times.

The tone waves generated by generator 3 are complex, containing the many harmonics required for production of the many tones or voices required in organ music. These harmonics are filtered and selected by a plurality of filter and tab controls 4-12 to yield the desired tone colors or voices. The waveshaping circuits of the kind shown in FIGS. 2-9 comprise the plurality of filter and tab controls 4-12. Since each separate type of filter and tab control (viz., 4-12) produces a distinctive tone coloration, the desired voices or tonal resources of the organ will determine which combinations of the several waveshaping circuits will be embodied 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.

The outputs of the several filter and tab controls (4-12) are combined in various combinations and supplied to respective output amplifier and expression 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 the 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.

As is known to those versed in the art, organs are frequently provided with devices called "couplers". These devices comprise a system of switching circuits associated with the key switches, whereby each key may play not only its nominal pitch, but also other pitches that are harmonically related to the 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 will permit the use of any conventional coupler system.

Referring now to FIG. 2, there is shown a typical waveform generator of the type comprising section II of generator 3 of FIG. 1. In this instance, the waveform from the frequency (master) source is a squarewave 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-front pulse 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 desired taper when working into a frequency flat filter, or one having 6 db/octave slope, a 12 db/octave slope, or any other desired slope. The output of the modified sawtooth may be channeled into two or more filters, each having any desired slope, and wherein each individual output is tapered to yield the desired musical characteristics, as will be described in connection with FIG. 5.

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 transistor to conduct. Bias is supplied 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 low-impedance load 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 31. The momentary turn-on of transistor 25, caused by the drive signal peaks causes the collector to draw a pulse of current, reducing the Vc-e to near zero and sends the energy stored in capacitor 34 into collection bus 35 which has a low impedance. This pulse of current stops suddenly the instant capacitor 34 is completely discharged, thus generating the desired rectangular 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 33 reduces 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 tone is achieved when transistor 25 conducts for roughly two to three times as long as it takes to completely discharge capacitor 34. This is only a small percentage of the operating cycle. The balance of the operating cycle is spent in recharging capacitor 34. Changing the ratio of the values of capacitor 34 and resistor 33 will change the waveshape of the sawtooth at a given frequency. Changing resistor 33 affects the amplitude of signal applied to collection bus 36, and changing capacitor 34 affects the amount of energy applied to collection bus 35.

When the key 27 is opened, the negative cut-off bias from the terminal 32 is restored, causing transistor 21 to not respond to the incoming "sync" pulses on line 21. Release envelope characteristics are controlled by the series combination of resistors 23, 24, 29 and capacitor 31. Capacitor 22 might have some effect depending on its value.

The main positive operating potential for the diapason generator is supplied via terminal 38 and resistor 37. The diapason tone signal on collection bus 36 is supplied to a filter 39 corresponding to one of the several filters 4-12 of the apparatus of FIG. 1.

It should 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 modification of 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 signal is derived 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.

FIG. 4 illustrates yet another modification of a waveform generator wherein the collector pulse of the transistor is isolated from the sawtooth waveform by means of a diode. This arrangement is desirable where the rectangular output pulse is to be derived from the collector of the transistor instead of, or in addition to, the output capacitor 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 circuit is likewise the 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 so that they can be tapered individually, such as required to produce open flute tones and for string tones. The number of outputs so tapered can be greater than the two shown. The collector of transistor 81 supplies collection bus 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 be connected to the positive supply terminal 89.

The circuits shown in FIGS. 4 and 5 may be combined to give a multiplicity of rectangular output pulses and modified sawtooth waveform outputs.

FIG. 6 illustrates the sharing of the keying control circuit with more than one diapason generator, allowing more efficient 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 to the base of transistor 93 via resistor 97. Similarly, the drive signal from another frequency source is supplied to transistor 98 via capacitor 99 and resistor 101. Bias to transistor 98 is obtained from terminal 96 via resistor 102. The release envelope is controlled by the series combination of resistors 103, 95 and 97 in parallel with the series combination resistors 104, 101 and 102, 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 105 via resistor 106. Operating potential is supplied from positive terminal 108 through resistor 104. The pulse storage capacitor 109 supplies the rectangular output signal to collection bus 111, and a low-impedance load is provided by resistor 112. Similarly, the sawtooth generated by transistor 98 is supplied to collection bus 114 via resistor 115. Bus 114 connects to the positive terminal 108 via resistor 116. Capacitor 117 sends the rectangular output pulse to bus 118, to which is connected load resistor 119. Filters 113 and 121 are energized by busses 105 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.

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 occur during the initial speech period of a flue organ pipe. The presence of such a sound results in clearly discernable articulation of the speaking stop. Generally speaking, the principal 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 generated by the pipe during steady-state operation. In certain pipes, the transient comprises a temporary increase in amplitude of certain harmonics of the keyed note. In diapason pipes, it can be observed that a tone one octave higher appears before the steady-state condition is reached. In certain other kinds of pipes, the chiff transient may be a still higher harmonic. In other cases, a lower than normal pitch comprises the desired chiff sound. Chiff sounds may be synthesized by momentarily "coupling" an available signal from another tone generator to the keyed note so as to cause the coupled signal to "speak" for the brief interval at the onset of the keyed note. The previously-described 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 generator as easily as from a like generator. The chiff pulse is supplied to the unit rank adapted to chiff by the diapason generator by lifting the grounded end of capacitor 31 as it appears in the circuits of FIG. 2, FIG. 3, or FIG. 5 and connecting it instead to the indicated point in FIG. 7. This point is identified as point 122 in FIG. 7. Note that the keying voltage must be removed from the diapason generator when the stop is not drawn to avoid the possibility of having a chiff sound audible with no note speaking.

The circuit of FIG. 7 is generally similar to those described previously in connection with FIGS. 2-6, and comprises a transistor 123 which receives a sync signal from its associated master oscillator via resistor 124.

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 sufficiently 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 is changed, 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 the 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 the time 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 is not desired, return the end of capacitor 133 to ground as indicated in FIG. 7. The waveform appearing on collection bus 134 will be a squarewave with the positive-going portion being somewhat rounded due to the loading of the other two waveform subcircuits. If more "rounding" of the waveform is desired, which adds even harmonics, capacitor 135 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 "woodiness" 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-going half cycle. This is accomplished by transistor 123 discharging capacitor 141 through diode 142 when transistor 123 saturates. When the transistor 123 cuts-off, capacitor 141, being decoupled by diode 142, recharges through resistor 143. The harmonic content is between the two above described waveforms.

The waveform 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 waveform on 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 on collection bus 144 and/or 147 is not required, then 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 busses 136 and 147 are not required, omit capacitor 149, diode 138 and resistor 152. If the waveforms on collection busses 139 and 144 are not required, omit capacitor 141, diode 142, resistor 143 and resistor 146. If the waveforms on collection busses 139 and/or 144 only, are required, omit capacitors 149, 135, diodes 142, 138 and resistors 152 and 153. Diode 142 is replaced by a solid connection, since its isolating function is not needed under this circumstance.

If the waveform on collection bus 131 is intended to generate a flute tone, and no clarinet tone is required, a fuller tone can be secured for certain types of flute tones (after filtering) by adjusting capacitor 135 for the desired amount of harmonic distortion. If the flute is to be sustained for percussive effects, this is desirable since there is some distortion on decay, and this can be matched for steady-state conditions so that the tone decays with a minimum of harmonic change. An added advantage of using capacitor 135 is that it increases the attenuation by by-passing the collector-to-base capacity of transistor 123 to ground.

Another (though less satisfactory) method of distorting the modified squarewave on collection bus 134 is to partially bypass the base of transistor 123 to ground 154 so that the input squarewave is rounded. This causes the cut-off time of transistor 123 to increase, and the turn-on time to decrease in a given cycle. This arrangement creates an interesting waveform, but on sustain, the increase in harmonic distortion is greater than with no modification. This also changes the waveforms at busses 136 and 139 somewhat, as does adding capacitor 135.

A third method of harmonically enriching the modified squarewave is to feed a small amount of signal into collection bus 134 from either (or both) of the other collection busses, or this may be accomplished in the voicing and mixing process.

FIG. 8 shows an alternate embodiment of the multiple waveform generator with chiff, in which a common-base 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 equivalent of resistor 124' in FIG. 8. Other components found in the circuit of FIG. 8, not having functional equivalents in the first-described circuit, carry unique indicia.

On long sustain, any key (e.g., key 127') being closed will raise the sustain bus 157 to the keying voltage potential. On short sustain, (or "reverb" sustain), resistor 155 and diode 156 will snub the release envelope down 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 157 is grounded to 154' or biased close to ground potential (either + or -) and the 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 operates in the same manner as described previously, and is adjusted the same; it can also be omitted in the same manner, as previously described. The addition of resistor 155, diode 156 and "sustain" bus 157 and switch 158' circuits to the apparatus of FIG. 7 as connected to the "key" end of resistor 132 will equip the first-described embodiment with variable-length sustain feature.

It is realized that the circuits of FIGS. 7 and 8 contain one more resistor than is absolutely needed if the operating voltages are specifically adjusted for the circuit, but the circuit shown conforms to a practical construction.

As was shown in the circuit of FIG. 6, two or more multiple waveform generators with chiff can be connected to share resistor 132 (or 132') and capacitor 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 (or 131') and capacitor 141 (or 141'). Sustain times in these circuits will be approximately equal. The chiff does not have to be limited to one note; two or more notes may be chiffed to really put the "Ch" in the chiff. This is shown in the embodiment of FIG. 9 and is accomplished by feeding the chiff pulse to the desired notes, while isolating the notes with diodes.

Referring to the circuit of FIG. 9, the sounding generator comprises transistor 161 which receives its sync signal via resistor 162. The output to the collection bus circuit is via resistor 163. Chiff pulses from other notes are applied via a matrix of diodes 164-165 to point 166. Resistors 167-170 functionally correspond to resistors 129, 131, 150, and 170, respectively, of FIG. 7. Capacitor 160 corresponds to capacitor 126 of FIG. 7. Resistor 140 corresponds to resistor 125. The keying voltage is obtained via key 172. The chiff drive signal is obtained via capacitor 173 (which functionally corresponds to capacitor 133 of FIG. 7). Resistor 174 is required to allow charging and discharging of capacitor 173.

The first 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 (").

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 those skilled in the art that numerous other modifications and variations may be made in the form and construction thereof without departing from the disclosed fundamental principles of the invention. It is therefore desired, by the following claims, to include within the 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.