Title:
ELECTRONIC MUSICAL SYNTHESIZER
United States Patent 3808344


Abstract:
An electronic musical synthesizer is provided with a radio frequency master oscillator which operates through a plurality of parallel divider paths of different dividing ratios to produce oscillations corresponding to the 12 musical notes of one octave. The divider circuits further operate through a divide by 2 circuit to produce a second octave plus one of musical tone frequencies, thus providing two octaves plus one of musical tones. The tones are played monophonically from a 25 note keyboard through a pair of priority latching networks. Further divider chains are provided which produce available notes in musical third and musical fifth relationship to the original notes, as well as notes in octave relation thereto. Various manually operable controls are manipulable by the musician to simulate known musical effect, and also to vary attack and decay, to vary the onset of a tone as to pitch, and to provide various modulations, thereby producing novel musical effects.



Inventors:
Ippolito, Anthony C. (North Tonawanda, NY)
Mcnerney, Roger J. (North Tonawanda, NY)
Schwartz, Harold O. (North Tonawanda, NY)
Application Number:
05/230295
Publication Date:
04/30/1974
Filing Date:
02/29/1972
Assignee:
WURLITZER CO,US
Primary Class:
Other Classes:
84/701, 84/703, 84/DIG.22, 984/311, 984/339, 984/348, 984/381
International Classes:
G10H1/053; G10H1/043; G10H1/22; G10H1/38; G10H5/06; (IPC1-7): G10H5/06
Field of Search:
84/1
View Patent Images:



Other References:

R G. Hibberd, Integrated Circuits, Texas Instruments Electronics Series, McGraw-Hill Book Company, copyright 1969, pp. 1-11..
Primary Examiner:
Wilkinson, Richard B.
Assistant Examiner:
Witkowski, Stanley J.
Attorney, Agent or Firm:
Olson, Trexler, Wolters, Bushnell & Fosse, Ltd.
Claims:
1. An electronic musical instrument comprising means for generating electric oscillations corresponding to musical tones and comprising two substantially parallel channels, a keyboard having at least two discrete parts, means connecting said oscillation generating means and said keyboard for effecting manual control of said oscillation generating means, and further means interconnecting said keyboard and said channels for respectively rendering one channel operable and the other inoperable depending upon which part of said keyboard is played on, operation of a key of said keyboard providing an input to both channels, the means for respectively rendering one channel operable and the other inoperable including means for enabling one of said channels and disabling the other.

2. An electronic musical instrument as set forth in claim 1 wherein each channel includes divide by 2 means to produce octave note frequencies and further includes additional frequency changing means to produce note

3. An electronic musical instrument as set forth in claim 2 wherein the frequency changing means of at least one channel includes divide by 3

4. An electronic musical instrument as set forth in claim 3 wherein at least one channel includes a multiply by two means in series with a divide

5. An electronic musical instrument as set forth in claim 2 wherein the two channels together among said additional frequency changing means include

6. An electronic musical instrument as set forth in claim 5 wherein the means for producing the three note frequencies in chordal relation produce

7. An electronic musical instrument comprising a master oscillator operating at a frequency above audio range, a plurality of parallel frequency divider means connected to said master oscillator and including frequency dividing means of different dividing ratio, to produce 12 frequencies which are multiples of the frequencies of the semi-tones of a musical octave, a keyboard having a plurality of keys, a frequency transmission network having at least 12 paths each having an input and an output, said 12 frequencies respectively being connected to said inputs, means connecting each of said keys to said network paths, each key on depression rendering its respective path conductive, all other paths being rendered nonconductive, means continuing the last operated path in conductive condition until a subsequent path is rendered conductive and thereupon rendering all other paths nonconductive, and frequency dividing means connected to said output to provide note frequencies in octave

8. An electronic musical instrument as set forth in claim 7 including two similar frequency transmission networks, the 12 frequencies being connected direct to one of said networks and through divide by 2 circuit means to the other of said networks whereby the outputs of said networks are in octave relation to one another, said keyboard having at least two parts respectively connected to said frequency transmission networks, and wherein there are two frequency division means respectively connected to

9. An electronic musical instrument as set forth in claim 8 and further including means interconnected with the two parts of the keyboard and with the two frequency dividing means for respectively rendering one of said frequency dividing means operative and the other inoperative depending

10. An electronic musical instrument as set forth in claim 7 wherein the frequency divider means has at least two dividers of different dividing ratio to produce at least two note frequencies in musical chordal

11. An electronic musical instrument as set forth in claim 8 wherein the two frequency divider means together have a plurality of dividers of different dividing ratio to produce at least three note frequencies in

12. An electronic musical instrument as set forth in claim 7 and further including feedback means from said frequency transmission network to said master oscillator to effect variation of the frequency of said master

13. An electronic musical instrument as set forth in claim 12 wherein the

14. An electronic musical instrument as set forth in claim 12 wherein the frequency varying means produces repetitive detuning of the master

15. An electronic musical instrument comprising a case having therein means for producing electric oscillations corresponding to musical tones, keyboard means on said case operably interconnected with said oscillation producing means for controlling said electric oscillations, said keyboard means having a predetermined width across said case, an additional keyboard on said case lying above and behind said keyboard means, additional electronic oscillation generating means in said case operably interconnected with and controlled by said additional keyboard, and manually operable controls on said case to at least one side of said additional keyboard and operably connected to said additional generating means for controlling the character of oscillations from said additional electric oscillation generating means, said additional keyboard being of lesser width than said keyboard means and being substantially centered relative thereto, said additional keyboard including a plurality of keys each manually depressable to a normal first position, and further being depressable past said first position to a second position, and means activated by movement of a key to said second position and interconnected with said additional electronic oscillation generating means to effect a predetermined variation in the characteristics of oscillations generated

16. An electronic musical instrument comprising a case having therein means for producing electric oscillations corresponding to musical tones, keyboard means on said case operably interconnected with said oscillation producing means for controlling said electric oscillations, said keyboard means having a predetermined width across said case, an additional keyboard on said case lying above and behind said keyboard means, additional electronic oscillation generating means in said case operably interconnected with and controlled by said additional keyboard, and manually operable controls on said case to at least one side of said additional keyboard and operably connected to said additional generating means for controlling the character of oscillations from said additional electric oscillation generating means, said additional keyboard being of lesser width than said keyboard means and being substantially centered relative thereto, said additional electronic oscillation generating means comprising a single master oscillator and a plurality of parallel frequency dividing means of different dividing ratios to produce a plurality of frequencies bearing musical note relation to one another, and a plurality of divide by 2 chains of frequency dividers connected to and controlled by said parallel dividing means to produce frequencies having

17. An electronic musical instrument as set forth in claim 16 and further

18. An electronic musical instrument as set forth in claim 17 wherein said additional keyboard includes a plurality of keys each depressable to a first predetermined position, and each further being depressable beyond said first predetermined position to a second predetermined position, and means activated by a key depressed to second position and interconnected

19. An electronic musical instrument as set forth in claim 17 and further including means interconnected with said keyboard and with said master oscillator to detune said master oscillator momentarily upon depression of any key of said additional keyboard.

Description:
In the past it has been common practice to design electronic musical instruments in such manner as to simulate or attempt to simulate known musical effects. This has been accomplished to a greater or lesser degree of success depending on the design of an individual instrument. More lately, efforts have been made to synthesize musical tones of somewhat novel nature. Such instruments have generally been rather complicated and cumbersome, and in at least many instances it has been necessary to play only one note or combination of notes at a time for purposes of recording, following which connections and controls are changed to allow recording of a subsequent note or combination of notes. This has precluded live performances with the results available only as recordings.

In accordance with conventional electronic instruments, specifically electronic organs, it is common practice to provide twelve master oscillators generating the 12 semi-tones of an octave, specifically the highest octave of notes to be played on the organ, or perhaps an octave higher. Divider chains or slave oscillators have been provided which have respectively been controlled by the master oscillators to produce similar notes in descending octave relation. It has long been known in theory that a single master oscillator could be employed with parallel dividers of different ratios of division to produce the 12 semi-tones of the top octave. This would have the advantage of requiring the tuning of only one master oscillator, a substantial production advantage. However, with electronic components as they existed until recently the cost and space requirements have been prohibitive. However, with the advent of LSI (large scale integration) it has become feasible to put this theory into practice. How to handle the note frequencies so produced is another matter, and forms a significant portion of the present invention.

In accordance with the present invention, a single master oscillator at a high radio frequency, on the order of 1.5 MHz is employed. This master oscillator is applied to the input of an LSI divider chain, having a plurality of parallel dividers of different divide down ratios, whereby 12 outputs are provided having the relation to one another of the 12 half tones of a musical octave. The output of the LSI divider chain is applied directly to a switching network, hereinafter identified as a priority latching network, and the output is also fed to a divide by two divider stage, and on to another priority latching network, whereby two octaves of frequencies are produced corresponding to musical tones. Further divider chains are fed by the outputs of the two priority latching networks to produce frequencies bearing relations to one another of musical thirds and fifths, as well as octave relations.

Various circuits are provided for controlling the attack and sustain or decay time in accordance with the desires of the musician. Means under the control of the musician also is provided for modulating the musical tones produced by the instrument at a desired low audio rate, the rate and extent of modulation being manually controllable. The keyboard is also provided with a "second touch" whereby, when a key is depressed beyond its normal depress position it will actuate a switch to produce still further effects, such as modulation for as long as the key is held down, or a crescendo or slide effect. Means also is provided under the control of the musician for producing a wah-wah effect as is often used in trumpet playing, and further manually controllable means is provided for effecting the shift of pitch at the onset of each tone.

Various objects and advantages of the present invention as well as circuits by means of which these are obtained will be apparent from a study of the following specification when taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of an electronic musical instrument constructed in accordance with the present invention;

FIG. 2 is a block diagram illustrating the principles of the present invention;

FIG. 3 is a layout of the stops and controls for the keyboard and effects forming the present invention;

FIG. 4 is a detail block diagram illustrating details of the present invention;

FIG. 5 is another detail block diagram illustrating further details of the present invention;

FIG. 6 is yet another detail block diagram illustrating details of the present invention;

FIG. 7 is a combination block and electronic wiring diagram illustrating a portion of the present invention;

FIG. 8 is yet another detail block diagram illustrating further aspects of the present invention;

FIG. 9 is an electronic wiring diagram illustrating a detail of the present invention;

FIG. 10 is a schematic wiring diagram illustrating a specific part of the present invention;

FIG. 11 is a schematic wiring diagram of the master oscillator and related parts;

FIG. 12 is a schematic wiring diagram of the steering circuit which determines which priority latching network output will be effective;

FIG. 13 is a partial block and partial schematic wiring diagram showing details of the modulation effect;

FIG. 14 is a schematic wiring diagram illustrating the percussion sections of the present invention; and

FIG. 15 is a schematic wiring diagram illustrating the attack and decay controlling circuits.

Referring first to FIG. 1, there is shown an electronic organ 20 having a case 22 with an upper keyboard 24 and a lower keyboard 26 in shortened, overlapping fashion, of the type generally known as a spinet organ. A suitable loudspeaker system is provided behind a grill 28 below the keyboard, and the organ is also provided with a one octave pedal board or clavier 30 and a swell pedal 32 for controlling overall volume. In addition, and generally in accordance with conventional practice, the organ is provided with stop tablets 34 generally on a level with the keyboards 24 and 26. Further, and also in accordance with conventional practice, the organ is provided with a music rack 36.

Departing from conventional practice, the organ is provided with a two octave plus one third keyboard 38 for producing novel effects, i.e. synthesizing. It is this keyboard and the accompanying synthesizer that form the subject matter of the present invention. Stop tablets 40 are provided to the left of the keyboard 38 for operation and control of the synthesizer in conjunction with the keys. Additional controls 42 for the synthesizer are provided to the right of the third keyboard 38.

Attention next should be directed to FIG. 3 for further illustration of the stop tablets 40 and the controls 42. As will be seen in FIG. 3, the stop tablets 40 from the left comprise nine sine wave tablets 44 of different footage lengths running from 16 foot through 11/3 foot. As is indicated in FIG. 3, these stop tablets comprise blue letters on a white background. Following the footage stop tablets 44 are three stop tablets 46 controlling filters for the usual three families of organ or orchestral sounds, namely reed, brass, and string, omitting the organ diapason which is generally considered to be the fourth organ family. For ready distinction to the player, the three stop tablets 46 comprise white printing on a red background.

To the right of tablets 46 there are disposed seven stop tablets, comprising red print on light yellow background, each representing a percussive sound, as labeled in the figure. As will be understood, all of the stop tablets 40, including the three groups 44, 46 and 48 control filters for producing the different preset effects indicated. More about this will be set forth later.

Turning now to the controls 42 on the right of the third keyboard, these will likewise be seen in FIG. 3, wherein it will be apparent that the straight line arrangement of the organ keyboard, stop tablets, and controls has been broken for simplicity of illustration. Reading from the left, there first will be seen a volume control 50 for the sine wave footage voices, with controls 52 and 54. The controls 52 and 54 comprise push buttons, the "bright" push button 52 making the timbre bright by increasing the highs, and the "deep" push button 54 making the timbre deep by increasing the lows.

The next section relates to a modulator which varies the pitch of any given note in the third keyboard, automatically raising and lowering it to selective heights and depths at a selected speed. To this end, there is a control knob 56 for a rheostat which sets the repetition rate of the modulator, while another knob 58 controls another rheostat to determine the extent of deviation of pitch. A push button 60 permits the modulator to be turned on and off.

Attack time is controlled by a knob 62 permitting the player to obtain at his will a fast attack, a slow attack, or anything in between, thus permitting the crisp playing of brass or percussion instruments, or the breathiness of a woodwind. As a correlary to the attack time, sustain time is controlled by a knob 64 which allows the performer to add various lengths of sustain to any sound on the third keyboard, including the percussion presets of the stop tablets 48.

Second touch is provided on the third keyboard. If any one of the keys of the third keyboard 38 is depressed its normal extent, the tone plays in normal fashion. A bail switch is provided beneath the third keyboard so that a key may be pressed down beyond its normal depth to produce a special effect. Two special effects are provided, namely a special turning on and off of a modulator, this effect being brought into play by a push button 64 to provide operation of the modulator only when the key is pressed below its normal stop depth. Alternatively, a push button 66 allows a slide or glissando effect, namely a detuning flat followed by the note coming up to its normal frequency as the key is depressed beyond its normal stop depth. A push button 68 is provided to turn the attack time on, while a push button 70 allows the sustain time control to be turned on.

Another push button 72 is provided for turning on delta pitch, the terminology being taken from mathematics and somewhat akin to differentiation. In particular, the delta pitch control allows each note played on the third keyboard to start below its nominal pitch and then to swoop up to the actual pitch, producing novel electronic effects not related to traditional instruments. One further push button 74 is provided for producing a wah-wah effect which is added to the reed, brass, and string voices of the filters controlled by the stop tablets 46 for realistic instrumental effects, or for use in conjunction with other voices for unusual, synthesized sounds.

Finally, the controls 42 include a knob 76 controlling a rheostat which permits the performer to adjust the overall volume of the third keyboard with any voice or combination of voices on the organ. Now that some indication has been given as to the effects that are to be obtained by the third keyboard, attention is invited to FIG. 2 for an illustration in block diagram form of how such effects are obtained.

The third keyboard is provided with a single master oscillator 78 operating at a radio frequency, specifically on the order 1.5 MHz. The output of the master oscillator 78 is applied to a large scale integrated circuit divider 80 having a plurality of divider circuits in parallel to provide an output at 82 corresponding to the 12 note frequencies of the top octave of semi-tones to be played by the third keyboard. The divider 80 comprises a L.S.I. chip or chips sold by General Instrument Corporation, Microelectronic division of Hicksville, N.Y. The divider 80 initially comprised two chips identified commercially by Wurlitzer Part Nos. 658579/651055 and 658580/659056, and also as General Instrument Corporation Part Nos. 76194 and 76195. The 12 outputs at 82 are connected to a first priority latching network 84.

A similar 12 note output appears at 86, the latter being connected to a divide by 2 divider circuit 88 which divides all of the notes by 2, and divides the one top note a second time by two, thus providing 13 outputs at 90 connected to a second priority latching network 92.

Frequency variable effects are provided at 94, including the modulator previously discussed, slide, delta pitch, wah-wah, and also vibrato. Such effects are connected at 96 to the master oscillator 78 to modulate the master oscillator. A feedback circuit is provided at 98 from the priority latching network 84 for controlling the delta pitch effect, as will be discussed hereinafter.

A high bus rod 100 and a low bus rod 102 are provided as part of the third keyboard 38. Twelve whisker wire contacts 104 corresponding to the top 12 notes D through C are individually engageable with the high bus rod 100 and are connected to 12 inputs of the priority latching network 84. Similarly, there are 13 whisker wire contacts 106 engageable individually with the low bus rod 102 corresponding to the thirteen lowest notes C through C. The whisker wire contacts 106 are individually connected to the priority latching network 92, and the corresponding note contacts are connected in parallel as indicated by the wires 108.

The priority latching networks are similar to the pedal latching networks which have for some years used in the Wurlitzer model 4300D organs. Somewhat similar networks are shown in Robert D. Barry Pat. No. 3,422,208 and Harold O. Schwartz et al. Pat. No. 3,480,719. Each priority latching network is provided with high note preference, and the higher octave priority latching network has preference over the lower octave. If any one note key is depressed for a particular priority latching network, say for example for the high priority latching network 84, that note will play and will continue to play even though the key is released, until another key is depressed which cancels the first note latched in, the second played note then continuing until another note is played, etc. As indicated, should the musician depress two keys at the same time, the highest key note will have preference.

The high bus rod 100 is connected at 110 to a steering circuit 112, and the output at 110 continues at 114 to a spike amplifier 116. The production of a spike upon closing of a key switch is well known in the art, see for example Harold O. Schwartz et al., Pat. No. 3,340,344. The spike so produced may be used to key rhythm effects, etc. Similarly, the low bus rod 102 is connected at 118 to the steering circuit 112, and also to the spike amplifier 116.

The output of the priority latching network 84 at 120 is connected to a junction 122 leading through a resistor 124 to a control point A. The control point A is connected through a resistor 126 to a junction 128. From the junction 128 connection is made to a "G" divider chain 130, leading to a keyer 132. The keyer is provided with an output at 134 leading to filters 136. The output of the filters 136 is applied to an amplifier 138 which feeds a loudspeaker or loudspeaker system 140.

The junction point 128 also is connected to a frequency multiplier circuit 142 which multiplies the frequency by two, and this is in turn connected to a divide by three circuit 144 leading to a "C" divider chain 146, the output of which is connected to a keyer 148 leading to the filters 136. The outputs of the divider chains 130 and 146 are in the relation of musical note G to musical note C. It will be understood that the input to the G divider chain 130 can be anything from B through C, and is not necessarily G, the important thing being that the outputs of the dividers 130 and 146 have the relation of G and C.

Returning to the priority latching network 84, and specifically the output 120 thereof, the junction 122 is further connected to a resistor 150 leading to a control point B which in turn is connected to a resistor 152 to a junction point 154. The junction point 154 is connected to a divide by two circuit 156 to a G divider chain 158, the output of which is connected to a keyer 160, and then on to the filters 136.

The junction point 154 is also connected to a divide by three circuit 162 to a C divider chain 164 and out through a keyer 166 to the filters 136.

Turning now to the priority latching network 92, the output thereof at 168 is connected to a junction point 170. The junction point 170 is connected through a resistor 172 to a control point A', with connection from the control point being through a resistor 174 to an "E" divider chain 176, the output of which is connected through a keyer 178 to the filters 136.

Connection is made from the junction point 170 also to a divide by two circuit 180 which is connected through a resistor 182 to a control point B'. The control point B' is connected through a resistor 184 to another E divider chain 186 which is connected through a keyer to the filters 136. It should again be noted that the E divider chains do not necessarily produce a frequency corresponding to the frequency of any E note, but bear the relation of a musical note E to the notes of the G divider chains 130 and 158 and to a musical C note as in the divider chains 146 and 164.

The steering circuit 112 is provided with two outputs 190 and 192. The output 190 is connected to the control points A and A', while the output 192 is connected to the control points B and B'. The outputs 190 and 192 are alternatively "go" and "no-go" outputs. Either will be go and the other no-go, depending on whether the musician plays a note corresponding to the high section of the keyboard and hence contacts a whisker 104 against the high bus 100, or vice versa. The output 192 is always exactly the opposite of the output 190, whereby a go signal is applied at control points A and A' with a no-go signal applied at points B and B', or vice versa. Thus, the steering circuit in cooperation with which of the buses is contacted determines whether the G, C, and E divider chains corresponding to the top octave or corresponding to the lower octave will play.

Reference now should be made to FIG. 4 with a further understanding of the effects produced by the controls 42. As noted heretofore in connection with FIG. 2 the master oscillator 78 is controlled at 96 from frequency variable effects 94. Specifically, and as implied in connection with FIG. 3 and the controls 42, the frequency variable effects comprise a slide effect applied to the master oscillator 78 on the line 194, and modulator effects applied to the master oscillator on a line 196. Considering first the slide line 194, it will be seen that this leads to a fixed contact 198 of a switch 200 having a movable switch contact 202 closed by the second touch bale 204. The movable contact 202 leads to a fixed contact of a normally open slide switch 206. When the slide push button 66 is depressed, the switch 206 is closed, and the side of the switch opposite to the switch contact 202 is grounded. Hence, whenever a key of the third keyboard 38 is depressed below its normal down position, it will depress the second touch bale to close the switch 202, and hence apply ground to the line 194 to detune the oscillator 78 slow or flat from its normal oscillating frequency. The detuning is sufficient that it will produce a half tone flat detuning in the audio frequency from the divider 80. When the key that has been depressed beyond its normal bottom position is released, the second touch bale 204 will rise, and the switch 202 will open, whereby ground is removed from the line 194, and the oscillator 78 comes back up to its normal frequency at a controlled rate.

The modulator line 196 has several connections to it, the first of which is a line 208 from the delta pitch switch 210, a normally open switch closed by the push button 72, and having applied to the opposite side thereof a signal through a delta pitch line from a delta pitch circuit 214 to be described hereinafter in some detail.

The modulator line 196 also has connected to it a line 216 leading to the second fixed contact 218 of the second touch bale switch 200. A second movable switch contact 220 is ganged at 222 with the movable switch contact 202, and the movable contact 220 is connected to the movable contact 224 of a normally open modulator second touch switch 226. The modulator second touch switch 226 is closed by the push button 64, and when it is closed, and the second touch bale 204 is lowered by pressing of a key below its normal down position, a signal is applied by way of the line 216 to the line 196, the signal being a varying signal.

The switch 226 is connected by means of a line 228 to a fixed contact 230 of a modulator switch 232. The switch 232 includes a movable arm or contact 234 normally engaging an open fixed contact 236, the switch arm 234 being moved into engagement with the switch contact 230 upon depression of the push button 60. When the push button 60 is depressed, the modulator effects are connected to the line 196 irrespective of the second touch bale position.

The fixed contact 230 of the switch 232 is connected by a line 238 to a sliding tab 240 on the potentiometer 242. The tab is controlled by the deviation knob 58. The bottom end of the potentiometer 242 is grounded, while the top end is connected to a modulator 244. The repetition rate of the modulator is controlled by a potentiometer 246, the sliding tab of which is controlled by the knob 56.

Turning from the special effects controls at the right side of the third keyboard to the stop tablet controls at the left side thereof, attention should be directed to FIG. 5. Footage filters for producing sine waves of the footage as illustrated in FIG. 3 is a simple and conventional matter. The oscillations throughout other than from the master oscillator are square waves, and these are filtered by active filters to produce sine waves. Hence, the footage sine wave details are not shown. However, the connections for the complex filters are shown in FIG. 5. Starting at the lower left corner, there is an eight foot amplifier 248 receiving the output of the C divider chain keyer 148 and supplying a bus 250. There is also a 16 foot amplifier 252 receiving the output of the lower C divider chain keyer 166, and supplying a bus 254. The bus 254 is connected to a reed filter 256 on the input side thereof, and also to the input of a brass filter 258. The outputs of both of these filters are connected to a bus 260. The bus 250 is connected to the input of a string filter 262, and the output of the string filter likewise is connected to the bus 260.

The bus 260 is connected to the movable contact 264 of a single pole, double throw switch 266 having two fixed contacts 268 and 270. The movable switch contact is controlled by the wah-wah push button 74, and in the normal, rest or idle position, the movable contact 264 engages the fixed contact 268. The fixed contact 268 is connected to a line 272 leading to a bus 274.

The fixed contact 270 is connected by means of a line 276 to a wah-wah filter 278. The wah-wah filter is controlled by a wah-wah keyer comprising a Schmitt trigger circuit 280 which receives a signal on the line 282 from the spike amplifier 116, whereby to provide a pulse of controlled width to the wah-wah filter each time a spike is supplied from the spike amplifier 116, i.e., each time a key is depressed. The output of the wah-wah filter 278 is connected to an amplifier stage 284 of a complex amplifier, and to an output line 286 leading to the amplifier 138. As will be seen, with the movable switch contact 264 in the idle position shown, the signal from the reeds, brass, and strings simply passes on the lines 272 and 274 to the amplifier 288, forming a part of the complex amplifier, and out on the line 286 to the final amplifier 138. On the other hand, when the wah-wah push button 74 is depressed, connection is made to the fixed contact 270, and hence to the wah-wah filter 278, whereby a wah-wah effect is impressed on the reed, brass, and string sounds, the output being through the amplifier 284 to the line 286 and on out to the final amplifier 138.

The output of the 8 foot amplifier 248 on the bus 250 is applied to a banjo filter 290, the output of which is connected to the bus 274. Similarly, the bus 250 is applied to the input of a harpsichord filter 292, and to the input of an electropiano filter 294, the outputs being connected to the bus 274.

The banjo, harpsichord, and electropiano filters just referred to comprise part of the filter group controlled by the stop tablets 48. The remaining stop tablets in this group comprise vibes 296, xylophone 298, glock (or glockenspiel) 300, and chimes 302. These are not connected to filters that are strictly complex tone filters, but are connected to the footage filters which are not specifically shown. The vibes stop tablet 296 comprises a control for a switching circuit which turns on the 8 foot filter and also momentarily a 2 foot filter to produce, respectively, a fundamental and a strike tone, as indicated at 304. Similarly, as indicated at 306, the xylophone stop tablet 298 controls the turning on of an 8 foot fundamental and a 22/3 foot strike tone. In like fashion, the glock stop tablet 300 controls a 4 foot fundamental and a 11/3 strike tone as indicated at 308. Finally, the chimes stop tablet 302 turns on the 6-2/5 foot, the 4 foot and the 22/3 foot filter, plus a short time turn on of a 2 foot filter as a strike tone, as indicated at 310. The outputs of the filter sets at 304, 306, 308 and 310 are connected direct to the amplifier 138, as are all of the footage filters comprising part of the filters 136.

Keying voltage switching for the various percussive stops is shown in FIG. 6. The switching is typical, and certain distinctions as to which of the specific stop tablets 48 is operated will be discussed. Starting at the lower left-hand corner of FIG. 6, a spike is supplied from the spike amplifier 116 to a Schmitt trigger circuit 312 which, when turned on, supplies a controlled positive spike out on line 314. The Schmitt trigger circuit 312 normally is biassed so as to be inoperative. However, the Schmitt trigger circuit is controlled as to operation through a capacitor 316 to a plurality of switches 318, all of which are on-off switches, and are normally open. One of these switches is shown as being typical, and for example, may be associated with the banjo stop tablet. When the banjo stop tablet is operated, the switch 318 is closed to complete a circuit to ground from the Schmitt trigger circuit 312 through the capacitor 316 so that the Schmitt trigger will be operated to produce the spike on the output line 314.

The line 314 is connected to a junction point 320. From the junction point a line 322 leads to a fixed contact 324 of a single pole double throw switch having a movable contact 326. The switch 326 again is duplicated, and the one shown is typical of switches associated with all of the percussive stop tablets 48. The movable switch contact is connected, depending on the switch which is under consideration, to keying diodes 328 associated with the 11/3 foot stop for producing the glockenspiel tone. Alternatively, and depending on the switch selected as typical, connection will be made to keying diodes 330 connected to the 22/3 foot keyer for producing xylophone effect, or to keying diodes 332 connected to the two foot stop for vibes or chimes. The keying diodes 328 are labeled as KG, since the keying is to the high G keyer 132. The keying diodes 330 are labeled as KX, and are connected both to the high G keyer 132 and to the low G keyer 160. The keying diodes 332 are labeled KV, comprising the high C keyer 148 and the low C keyer 146. With the movable switch contact 326 in the raised position shown, the short spike on the line 314 is not applied to any of the keying diodes 328, 330 or 332.

The junction point 320 also is connected by a line 334 to one fixed contact 336 of a sustain switch 338 having a movable contact 340 controlled by the sustain on push button 70. In the raised position shown the sustain is off. The movable switch contact is connected by a line 342 to a fixed contact 344 of a banjo switch 346 having a movable contact 348 controlled by the banjo stop tablet comprising one of the stop tablets 48. The movable switch contact 348 in the raised position shown engages a fixed contact 350 which is connected to a junction point 352. The junction point is connected to an input line 354 receiving a pulse 356 having a sharp leading edge and a decaying trailing edge. The width of the pulse 356 and the character of the trailing edge are controllable, and the source of this pulse will be set forth at a later point herein.

The junction point 352 also is connected by a line 356 to the second fixed switch contact 358 of the sustain switch 338.

The movable switch contact 348 is connected to a line 360 leading out to keying diodes 362, comprising part of the low G keyer 160 and of the low E keyer 188. The line 360 also is connected to the second fixed contact 364 engageable by the movable switch contact 326.

With the various switches of FIG. 6 in the position shown, there is no short spike from the Schmitt trigger keyer 312, and there is no place for such a spike to go if there were one. On the other hand, assuming that a pulse 356 is generated, it is applied to the keying diodes at 362.

If the banjo stop 48 is selected as the typical stop to be operated, then a pulse is applied on the line 314, due to closure of the switch 318. There is not a typical switch including the arm 326 corresponding to the banjo stop, so the pulse does not go anywhere in this direction. However, it does go on the line 334 to the switch 338, assuming the sustain is left off, and goes to the switch 346 which is now closed on the lower contact 344 and hence to the keying diodes 362, and hence to produce a short burst of banjo-like sound.

On the other hand, if it be assumed that the typical stop operated is not the banjo stop, but is one of the other stops associated with the stop tablets 48, and specifically one of the vibes, xylophone, glock, or chimes, then the short spike appearing on the line 314 will turn on the appropriate diodes 330, 328, 332 for a brief time. At the same time, the longer pulse 356 will be applied to the keying diodes 362 to produce the longer or fundamental tone. Other combinations upon operation of the various switches will be apparent to those skilled in the art.

Reference has been made heretofore to voltages applied to keying diodes, and a typical diode keying circuit is shown in FIG. 7. A frequency input is indicated at 366, and this could be the frequency input of any of the divider chains heretofore identified in connection with FIG. 2. The frequency input is to a divide by 2 circuit 368 having an output at 370 to the cathode of a diode 372. The divide by 2 circuit 368 also is connected in cascade with a second divide by 2 circuit 374 having an output at 376 connected to the cathode of a diode 378.

The anode of the diode 372 is connected to a junction point 380, and this junction point is connected through a resistor 382 to a biassing and keying voltage source 384 which normally is at a potential which is negative relative to the cathodes of the diodes 372 and 378 to bias the diodes off. The keying voltage also is connected through a resistor 386 to a junction point 388 which is connected to the anode of the diode 378 whereby both diodes are biassed off.

The junction point 380 also is connected through a resistor 390 to an output circuit 392 leading to filters as previously noted. Similarly, the junction point 388 is connected by means of a resistor 394 to an output line 396 also leading to certain of the filters previously mentioned. When a keying voltage is applied at point 384, both diodes 372 and 378 are biassed on so as to conduct signals from their respective divide by two circuits 368 and 374 to their respective filter output paths 392 and 396. Which of the two will sound, the oscillations being an octave apart, and hence corresponding, for example, to an 8 foot and a 16 foot pitch, depends on which filters are turned on by the respective stop tablets. The resistance of the resistors 382 and 386 is high enough compared with the resistance of resistors 390 and 394 that no substantial output from the divider 368 will appear on the output line 396, and vice versa.

The pulse appearing on line 98 at the inception of a note is used for attack and sustain control in connection with the circuit of FIG. 8. The signal on the line 98 is applied to an amplifier 398 which provides the gate signal shown below it as 400. This gate signal is connected to a junction point 402 and across a capacitor 404 to a junction point 406. The transition signal passed by the capacitor 404 to the junction point 406 is applied to another junction point 408, and from this to the top of a variable resistor 410 controlled by the attack knob 62. Specifically, the knob 62 controls the position of the slider 412 on the resistor 410. The slider 412 is connected to a fixed contact 414 of an attack-on switch 416 controlled by the push button 68. When the attack is off, the fixed contact 414 is open. However, when the attack is on, the fixed contact 414 is engaged by the movable contact arm 418 of the attack switch 416 whereby to convey the attack pulse signal to a junction point 420. This junction point is connected to an amplifier 422 to supply the keying voltage switching pulse 356 previously referred to in connection with FIG. 6. The value of the resistor 410 combined with the size of a capacitor 424 shunting the junction point 420 to ground determines the shape of the leading edge of the keying voltage pulse 356.

The capacitor 404 is parallelled by a pluck attack electric switch 426 connected to the junction points 402 and 406. The pluck attack electric switch is normally closed, but is opened by a potential appearing on a line 428 forming the output line of a DC amplifier 430, the input of which is normally open, but which is connected to ground by closing of a switch 432. There are six such switches, operable more or less in parallel, and each is closed by a respective stop tablet of the stop tablets 48 as indicated in FIG. 8, namely harpsichord, electropiano, xylophone, vibes, glock, or chimes. When the switch 426 is on, and this switch, by way of simple example, can be a transistor which is biassed to conduct or not to conduct, the DC level of the output of the amplifier 398 will be applied to the junction point 406, thus providing a different type of potential thereto than is possible through the capacitor 404.

The junction point 408 likewise is connected to a preset attack electric switch 434, the other side of which is connected to the second fixed contact 436 of the attack-on switch 416. The switch 434 normally is biassed for conduction by means of a normally closed grounded switch 438. Thus, normally the signal appearing at junctions 406 and 408 is applied without change to the junction point 420 at the top of the attack and sustain capacitor 424 and forming the input to the amplifier 422 to provide a preset rapid attack. When a typical switch operator is used to open the switch 438, the specific illustrative example being for the string stop tablet, the attack signal is not applied to the amplifier 422, and it will be appreciated that this is in keeping with a string sound which has a non-percussive type of inception.

In addition to the discharge path provided by the input to the resistor 422, the junction point 420 at the top of the attack and sustain capacitor 424 is connected to a discharge or sustain path 440. The path 440 leads to a junction 442 which is connected to a manual sustain circuit including a variable resistor 444 having a tap 446 thereon, the position of which is controlled by the sustain knob 64. The tap is connected to a fixed contact 448 of the sustain on switch 450, the movable arm 452 of which normally does not engage the fixed contact 448, but which is brought into engagement therewith upon depression of the sustain on push button 70. The movable contact 452 is connected by a line 454 back to the junction point 402, so that with the manual sustain on the capacitor 424 is in part discharged by the potential appearing at 402 when the gate signal 400 reverts to its normal state.

The sustain line 440 also leads to a junction point 456 which is connected through a resistor 458 to a junction 460 leading to the second fixed contact 462 of the sustain on switch 452. Thus, when the manually controllable sustain is not switched on, a preset sustain is provided by the resistor 458, qualified in that it may be parallelled by other resistors as hereinafter set forth.

The junction point 456 on the sustain line is connected to another junction point 462 which leads through a resistor 464 to a junction point 466. The junction point 466 is connected direct to a junction point 468, and this is connected through a resistor 470 to a junction point 472. A normally open medium sustain electric switch 474 is connected from the junction point 462 to the junction point 466, and is biassed by means of a line 476 to conduct, and hence to short out the resistor 464, whenever a grounded switch 478 is closed. There are three such switches in parallel, respectively being closed whenever the harpsichord, xylophone, or glock stop tablet is operated. In addition, there is a two pole normally open switch 480 controlled by the electropiano stop tablet, and whenever this is closed ground also is applied to the line 476 to close the switch 474.

A medium long sustain electric switch 482 is connected between the junction points 468 and 472 to short out the resistor 470 when the switch 482 is closed by the second pole of the electropiano switch 480.

A long sustain electric switch 484 is connected from the junction point 472 to the junction point 460 adjacent the sustain on switch 450. The switch 484 is biassed for conduction or non-conduction by a normally open grounded switch 486.

As will be apparent, if the sustain on switch 450 is in the off position as shown, and if the long sustain electric switch 484 is open, the sustain time is determined by the resistor 458. If the switch 484 is closed, then the resistor 458 is parallelled by the series combination of resistors 464 and 470, thereby providing a somewhat lower resistance, and shortening the sustain time. With the long sustain electric switch 484 closed, if the medium long sustain electric switch 482 conducts, it shorts the resistor 470, whereby the resistor 464 is in parallel with the resistor 458, producing a somewhat lower resistance, and a shorter sustain time. Similary, if the medium sustain electric switch 474 is in the on condition with the switch 482 open, then the resistor 470 is parallel with the resistor 458, presenting a somewhat lower resistance, and providing a medium sustain. On the other hand, if the sustain on push button 70 is depressed, the switch 450 is reversed in position, to remove all of the previously mentioned resistors and electric switches from the circuit, whereby sustain of the pulse 356 is determined by the variable resistor 444, as adjusted by the sustain knob 64.

The wah-wah filter 278 has been noted heretofore in connection with FIG. 5, and details on this filter will be seen in FIG. 9. The input line 276 is connected from the brass filter through the wah-wah switch 266 referred to in FIG. 5 to the input of the wah-wah filter 278 through a capacitor 488 shunted to ground by a resistor 490 in accordance with conventional practice. The input is connected to the base of a transistor 492, the emitter of which is grounded. The collector is connected through a resistor 494 to a positive voltage supply line 496. Voltage divider resistors 498 and 500 provide proper bias for the base.

Connection is made from the collector of the transistor 492 through a capacitor 502 to a junction point 504 on a voltage divider comprising a resistor 506 connected to the positive supply line 496 and a grounded resistor 508. Connection is made direct from the junction point 504 to another junction point 510 which is connected to a light dependent resistor 512, the other end of which is connected to a junction point 514. The junction point 514 is connected through another light dependent resistor 516 to the base of an N-P-N transistor 518, the collector of which is connected to the base of another transistor 520 in a Darlington amplifier configuration, the output being taken from the emitter of the transistor 520 through a resistor 522 to an output at 524. The emitter is grounded through a resistor 526.

The junction point 514 between the two light dependent resistors is connected by a capacitor 528 to the emitter of the transistor 520, being therefore nearly at DC ground potential. The base of the transistor 518 is shunted to ground by a predetermined value capacitor 530, and also by a capacitor 532, the value of which is selected from a predetermined group of values during production in order to compensate for other variables in the system, and to produce the desired results.

A connection is made from the voltage supply line 496 through a resistor 534 to a line 536 leading to one side of a lamp bulb 538, the other side of which is grounded at 540. Although this is shown conventionally as a tungsten lamp bulb 538, it will be appreciated that somewhat different types of results could be obtained with different types of light emitting sources, such as a light emitting diode. Finally, an input pulse is applied to an input line 542, 496 by a resistor 544, and also direct by means of a line 546 to the line 536 leading to the lamp bulb 538. The shape of the pulse applied on the line 542 from the Schmitt trigger 280 is shown at 548 at the upper left of FIG. 9.

Normally, the lamp bulb 538 burns at a predetermined level of illumination as determined by the voltage source supplied to the line 496 and by the value of the resistor 534, as well as inherent characteristics of the lamp bulb. The light from the lamp bulb 538 impinges on the two light dependent resistors 512 and 516. As will be recognized, if no light at all were on these resistors, they would be of a very high value. Since a certain level of light is on the resistors, they have a lower value, and conduct the input signal from the amplifying stage comprising the transistor 492. When a pulse from the Schmitt trigger is applied at the start of a brass tone, a greater voltage is momentarily applied to the line 536, raising the potential thereon from a nominal 7.5 volts by an additional 5.3 volts, thereby causing the lamp bulb 538 to burn at a higher level of illumination. This momentarily drops the value of the resistors 512 and 516, whereby to increase the level of the signal applied to the Darlington transistors 518 and 520. It will be recognized that the resistors 512 and 516 act with the capacitors 528 and 530, 532 as RC filter, the frequency characteristics of which are changed upon changing of the value of the resistors 512 and 516, thus producing a momentary frequency detuning as well as change in volume level whereby to produce the characteristic WAH sound at the start of a brass tone, as is used in playing a trumpet or the like with a wah-wah sound.

The delta pitch circuit 214 has also been referred to in connection with FIG. 4, and details on this circuit will be seen in FIG. 10. The pulse previously referred to as appearing on the line 98 upon the inception of playing of a tone is applied at 550 through a resistor 552 to the base of a transistor 554. The transistor is of the N-P-N type, and the emitter thereof is grounded. The collector is connected through a resistor 556 to a positive voltage supply line 558, and is also connected through a resistor network 560 and 562 to the base of an amplifying transistor 564, this transistor also being of the N-P-N type and having the emitter grounded. The collector is connected through a resistor 566 to the positive voltage supply line 558, and is also connected direct to a capacitor 568 of rather high value. For example, the capacitor 568 may be on the order of ten MFD. The opposite side of the capacitor 568 is shunted to ground by a diode 570, poled as shown with the anode connected to the capacitor and the cathode connected to ground. A resistor 572 is connected to the junction between the capacitor and the diode to provide the delta pitch output on the line 212.

As will be recognized, when the negative going pulse is applied on the line 550, conduction of the transistor 554 will suddenly increase, and that of the transistor 564 will suddenly decrease, thereby rapidly dropping the potential at the collector of the transistor 564. This, in turn, will very rapidly drop the potential on the output side of the capacitor 568, and the potential on the output side will rise to its normal quiescent level, producing a short pulse as illustrated at 574 in FIG. 10 which is used to detune the master oscillator momentarily to a somewhat lower frequency, thus producing a drop in pitch of each audio tone of approximately a half semi-tone at the inception of the playing of the note, followed by rapid return to the proper note frequency.

Attention now should be directed to FIG. 11 for a more detailed showing of the master oscillator 78. The oscillator includes an NPN transistor 576 the emitter of which is grounded. The collector is connected to a junction point 578 and through a resistor 580 to a positive voltage supply line 590. The collector also is connected back to the base through a resistor 592, and is connected through a capacitor 594 to the top of an inductance coil 596, the bottom of which is grounded. The top of the inductance coil also is connected by a capacitor 598 to the base of the transistor 576.

The slide line 194 is connected through a resistor 600 to the common input line 96 which leads to the base of the transistor 576. Similarly, the modulating or vibrato line 196 is connected through a resistor 602 to the common line 96.

It thus will be seen that there is an inductance-capacitance tuned oscillator, the constants of which are chosen to produce an oscillating frequency of 1.5 MHz. The oscillations produced are of a sine wave, and voltages applied to the base through the line 96 will produce detuning thereof to produce a slide, vibrato, etc.

The output of the oscillator 78 is taken from the junction point 578 connected to the transistor collector, and this is connected to a parallel combination of a resistor 604 and a capacitor 605 to sharpen the leading edge of the wave. The resistor-capacitor combination is connected to the base of an NPN transistor 606, comprising a buffer stage, and having the emitter connected to ground through a resistor 608. The collector of the transistor 606 is connected to a positive voltage supply line 610 through a resistor 612, and the collector is also connected through a capacitor 614 to the base of an NPN transistor 616 forming another buffer stage. The emitter of the transistor 616 is grounded through a resistor 618, and the output is taken from the emitter at 620, leading to the LSI divider 80. The collector is connected to a positive voltage supply source 622, and the base is also connected to this positive voltage supply source through a resistor 624.

Circuit details and operation of the steering circuit 112 will be seen with reference to FIG. 12. The line 110 from the high end of the bus 100 is connected through a resistor 626 to the base of an NPN transistor 628, having the collector thereof connected through a resistor 630 to a positive voltage supply at 632. The emitter is connected to a line 634 of which more will be said later. The collector further is connected through a resistor 636 to the base of another NPN transistor 638, the emitter of which is grounded through a resistor 640. The base also is connected to ground through a resistor 642, the resistors 636 and 642 being of equal and rather high value, as compared with the resistor 626, and particularly the resistor 640. The collector of the transistor 638 is connected through a resistor 644 to the line 118 from the low end of the bus 102. The emitter of the transistor 638 also is connected to a line 646.

The two output lines connected to the emitters of the transistors 628 and 638, namely 634 and 646, lead to a flip-flop circuit 648 comprising a pair of NPN transistors 650 and 652. The emitters of both transistors are grounded. The collector of transistor 650 leads to a junction point 653, and from thence through a resistor 654 to a positive voltage supply line 656. The junction point 653 also is connected through a resistor 658 to the base of the transistor 652.

The line 634 is connected to the base of the transistor 650, and this base is connected to ground through a resistor 660. The collector of transistor 652 is connected to a junction point 662, and from thence through a resistor 664 to the positive voltage supply line 656. As will be understood, the resistors 654 and 664 are of equal value. The junction point 662 also is connected through a resistor 666 to the base of transistor 650 and it will be understood that resistors 658 and 666 are equal to one another. Resistor 660 also is equal to resistor 640.

Junction point 653 is connected through resistors 668 and 670 to the bases of transistors 672 and 674, respectively. The emitters of both of these transistors are grounded. The collector of transistor 672 is connected to point A referred to in FIG. 2, while the emitter of transistor 674 is connected to point A', also referred to in connection with FIG. 2.

Junction point 662 is connected through a resistor 676 to the base of an NPN transistor 678, and also through a resistor 680 to the base of an NPN transistor 682. The emitters of both transistors 678 and 682 are grounded. The collector of transistor 678 is connected to point B in FIG. 2, while the collector of transistor 682 is connected to point B' in FIG. 2.

If a note is played on the high bus 100, then there is a positive signal in on the line 110, whereupon the transistor 628 conducts. This lowers the potential at the bottom of the resistor 630, and hence lowers the bias potential to the base of the transistor 638, whereupon the latter is cut off. Meanwhile, due to conduction of the transistor 628, a positive potential exists on the line 634, whereby the conductor 650 conducts. This lowers the potential at junction point 652 nearly to ground, thus to cut off transistors 672 and 674, whereupon points A and A' are floating, and whereupon the signal appearing at those points will pass on through the respective divider chains.

On the other hand, the ground potential at point 652, coupled with the relatively low potential on line 646 due to nonconduction of transistor 638 maintains the transistor 652 in nonconducting condition. Accordingly, there is a relatively high potential at point 662, and transistors 678 and 682 will conduct, thereby effectively grounding points B and B', and grounding out signals appearing at these points on FIG. 2. Thus, only the relatively higher frequency signals will be transmitted.

Conversely, if a note is played on the low bus 102, then a positive potential is applied at 118, and none at line 110. Thus, transistor 638 conducts while transistor 628 is off. Conduction of transistor 638 raises the potential at the top of resistor 640, and hence on line 646 to render transistor 652 conductive, thereby cutting off transistors 678 and 682, so that signals appearing at points B and B' will be transmitted. Conversely, the bias applied through resistor 666 to the base of transistor 650, combined with nonconduction of transistor 628, causes transistor 650 to be cut off. This raises the potential at point 652, and transistors 672 and 674 will conduct, thereby effectively grounding points A and A', whereby signals applying at points A and A' are grounded out, and do not pass on to the respective divider chains. Accordingly, only the lower octave is played.

A simplified generally block diagram showing effects control on the oscillator will be seen in FIG. 13. Thus, the master oscillator 78 again is shown with the input line 96. A vibrato oscillator 684, generally comprised within the modulator 244 discussed in connection with FIG. 4, is connected by means of an on-off switch 686 to the line 96, and varies the voltage applied to the base of the oscillator transistor as discussed in connection with FIG. 11, to cause the frequency of the master oscillator to rise and fall about the nominal oscillator frequency at a rate such as to produce a cyclic audio frequency variation of about 6 to 7 cycles per second.

A slide control comprises a potentiometer resistor 688 having one end thereof 690 maintained at a positive voltage with the opposite end 692 maintained at a negative voltage, the center thereof being grounded as indicated at 694. A slider 696 on the potentiometer may move either up to raise the voltage positive as picked off, or down to produce a negative voltage, the slider being connected to a collector line 698 leading to the oscillator input line 96, whereby to raise or lower the voltage on the base of the oscillator transistor, thus to detune the oscillator either sharp or flat, as may be desired.

Reference has been made heretofore to delta pitch, and also to the production of pulses upon closing of any key. A keying pulse amplifier, which may be the amplifier 116 previously referred to, is provided with two outputs. A positive output is applied at 700 to a series capacitor 702 leading to a junction 704. The junction 704 is connected to the anode of a diode 706 leading to a fixed switch contact 708 engageable by movable switch arm 710 connected to the collector line 698. The junction 704 further is connected to the cathode of a grounded diode 712. A positive pulse is passed by the capacitor 702 and by the series diode 706 to place a positive pulse on the collector line 698, thus momentarily to raise the voltage on the base of the oscillator transistor, and thus to raise the frequency slightly. Any tendency for a negative pulse to be passed by the capacitor 702 on the backside of the keying pulse is overcome by the diode 712 which shorts to ground in the negative pulse.

In addition, an output from the keying pulse amplifier 116 is applied to a 180° phase inverter 713 to provide a negative output pulse, and this is applied to a series capacitor 714 which is connected to the junction 716. The junction is connected to the cathode of a series diode 718 leading to a fixed switch contact 720 which is engageable by the movable contact arm 710 upon movement thereof away from the fixed contact 708. By this means a negative pulse can be applied to the collector line 698 into the input line 96 to the base of the oscillator transistor, whereby to detune the oscillator flat upon closing of any key. A grounded diode 722 has its anode connected to junction 716 to shunt to ground any positive pulse at this trailing edge of the spike or otherwise.

Finally, in FIG. 13, there is shown a wah-wah effect produced on the master oscillator rather than through the use of a filter at a later stage. A keying pulse amplifier 724 will produce an amplified pulse whenever a key is depressed, and this may be connected from the keying pulse amplifier 116, or otherwise. The amplifier will produce a positive going pulse 726 upon key closing, as shown, and will produce a negative going pulse 728 upon key release. The output including both such pulses is applied to a series capacitor 730, and preferably through an on-off switch 732 to the collector line 698. Thus, when any key is closed, the master oscillator is briefly detuned sharp, and when the key is released, the master oscillator is briefly detuned flat, thus to produce a wah-wah effect in the audio output.

A simplified wiring diagram for playing music or noises with controllable attack and sustain is shown in FIG. 14. An input line 734 is provided from a pulse amplifier similar to the pulse amplifier 116, and a negative going pulse is shown beneath it at 736. The line 734 is connected to the base of an NPN transistor 738, the emitter of which is grounded. The collector is connected through a resistor 740 to a positive voltage supply as indicated at 742, and the base likewise is connected through a resistor 744 to this positive voltage supply. The circuit produces a percussive effect, and the output of the transistor 738 is taken from the collector on a line 746, shunted to ground by a resistor 748. The pulse as amplified by the transistor 738 is applied over the line 746 to a series capacitor 750 leading to a junction 752 and shunted to ground by a diode 754 having the anode thereof grounded and the cathode connected to the junction 752. The junction 752 is connected to a series resistor 756 having a portion thereof shunted by a tap 758 and a line 759 leading back to the junction 752. The far side of the resistor 756 is connected to the anode of a diode 760, and the cathode thereof is connected to a junction 762.

A capacitor 764 shunts the junction 762 to ground, and the junction is connected to the base of an emitter follower NPN type transistor 766, having the output taken from the emitter as indicated at 768, and having the emitter grounded through a resistor 770. The collector of the transistor 766 is connected to a voltage source 772 which is selected as between plus zero and minus 22 volts.

The junction 762 is connected back to the line 746 by a diode 774 having the anode thereof connected to the junction 762 and having the cathode thereof connected to a resistor 776. A slider 778 is connected to the resistor, and a line 780 connected to the slider acts with the slider to short part of the resistor, the two being connected back to the line 746 by a line 782. The slider 758 controls the attack, while the slider 778 controls the sustain. A wave shape 784 is shown beneath the circuit, and it will be recognized that the rising part of the wave is determined primarily by the value of the resistor 756 and by the capacitor 764 as the capacitor 764 is charged, while the negative part is determined by discharge of the capacitor 764 through the diode 774, the sustain resistor 776, and the resistor 748. A switch 786 bypasses the capacitor 750, and when closed this switch holds the wave shape 284 at its peak until such time as the key is opened whereby music or noise is sounded as long a key is depressed. When the switch 786 is open, there is a percussion effect in which both attack and decay are controllable by the player, somewhat similar to that previously discussed in connection with FIG. 8.

Embellishments and improvements on the circuit of FIG. 14 are shown in FIG. 15. Most of the circuit is similar to that of FIG. 14, and similar numerals are used to avoid prolixity of discussion. Minor changes will be evident, such as inclusion of a resistor 788 in the input line 734 leading to the base of the first transistor 738. One distinction is that a signal is applied from either priority latching network 84 and 92 to the line 734 such that whenever any note is played the potential on line 734 drops from a positive 12 volts to ground.

There is also a resistor 790 incorporated in the return line from the sustain resistor 776 to the line 746. In addition, rather than a single output transistor, two transistors 792 and 794 are arranged in a Darlington circuit well known in the art.

The most significant difference is that the bottom of the capacitor 764 is not connected direct to ground, but rather is connected to a junction point 796 which can be grounded through an on-off switch 798. A resistor 800 shunts the junction 796 to ground, and a capacitor 802 also shunts the junction to ground.

Various types of wave shapes can be produced as shown at the bottom of FIG. 15. The wave shape 804 at the bottom left of FIG. 15 is produced with the "pluck" switch 786 open. The first portion 806 at the curve, the attack portion is determined by the charging time of the capacitor 764 and the effective resistance of the resistor 756 (assuming the percuss switch 798 to be closed). The central portion 808 of the curve is substantially at the supply voltage, and remains as long as the key remains on. When the key is released, the sustain portion 810 of the curve is produced as the capacitor 764 discharges through the diode 774 and resistors 776, 790, etc.

In the event that the pluck switch 786 is open, the capacitor 750 will pass a sharp pulse, very quicky producing a peak voltage as seen at 812 in the curve 814. The front portion of the curve would be rounded off to some extent if any residual value of resistance were left in the resistor 756, and the vertical front of the curve as shown is produced when the resistor 756 is entirely shorted out. The sustain portion 816 of the curve is provided upon discharge of the capacitor 764.

The third curve 818 is produced with the percuss switch 798 open. Again, the attack time is at a minimum so that the voltage rapidly rises to the peak at 820. However, the sustain portion 822 of the curve is somewhat different, having an initial very rapid drop portion 824 as the capacitor 802 discharges through the resistor 800, followed by a more gradual portion 826 as the capacitor 764 discharges.

We have now disclosed a novel electronic musical instrument comprising a synthesizer added to a generally conventional electronic organ. The synthesizer comprises an additional keyboard centered above and behind the usual keyboard, with controls for the additional keyboard disposed to either side thereof. These controls provide the musician with unprecedented control over the character and quality of the sound. Attack and decay characteristics are readily varied to suit the requirements of the musician. The pitch of notes can be modulated at will, the pitch of a note can be detuned at inception of each tone, and a wah-wah effect can be produced at will. The additional keyboard is provided with a second touch for controlling pitch variation, augmenting the effects noted above. Novel electronic circuits are utilized to produce the desired results.

The specific examples of the invention as herein shown and described are for illustrative purposes only, and various changes will be apparent to those skilled in the art and will be understood as forming a part of the present invention insofar as they fall within the spirit and scope of the appended claims.