US3916750A

US3916750A - Electronic organ employing time position multiplexed signals

Info

Publication number: US3916750A
Application number: US376189A
Authority: US
Inventors: Dale M Uetrecht
Original assignee: DH Baldwin Co
Current assignee: BPO ACQUISITION CORP; Baldwin Piano and Organ Co; DH Baldwin Co
Priority date: 1972-02-04
Filing date: 1973-07-03
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04

Abstract

An electronic organ including a counter acting as a source of twelve repetitive time position multiplexed signals, each derived at a different time on a different lead, one time position being provided for each note nomenclature of the musical scale, time positioned pulses being gated through respective key switches having the same nomenclature as respective time position slots. All time positioned signals passed by any octave of key switches are combined on a single octave output lead assigned to that octave, and signals on octave output leads are selectively combined by coupler logic, output signals derivable from the coupler logic network being combined with pulse position signals derived directly from the source to provide coincident gate signals which cause tone source signals to be fed via tone color filters to an output load.

Description

United States Patent 11 1 11] 3,916,750 Uetrecht 5] *Nov. 4, 1975 ELECTRONIC ORGAN EMPLOYING TIME 3,696,201 10/1972 Arsem et al. 84/1.01 S T MULTIPLEXED SIGNALS 3,697,661 10/1972 Deutsch.; 84/ 1.01 3,743,755 7/1973 Wats0n.... 84/101 Inventor: Dale M- Uetrechl, Clncmnatl, ohlo 3,746,773 7/1973 Uetrecht..... 84/1.01 3,755,608 8/1973 Deutsch 84/].01 [73] Ass'gnee' Baum Company cmcmnat" 3,763,364 10/1973 Deutsch et al 84/1.03 x

[ Notice: The portion of the term of this P i r Examiner-Stephen J. Tomsky P n q to y 17, 1990 Assistant ExaminerStanley J. Witkowski has been dlsclalmed- Attorney, Agent, or FirmHyman Hurvitz [22] Filed: July 3, 1973 21 App]. No.: 376,189 [57] ABSTRACT I An electronic organ including a counter acting as a Related Apphcahon Data 7 source of twelve repetitive time position multiplexed [62] Dlvlslo" 223,629, 4, 1972, signals, each derived at adiiferent time on a different lead, one time position being provided for each note nomenclature of the musical scale, time positioned [52] US. Cl.2 84/]..01; 8471.03; 84/117 pulses being gated through respective key Switches [51] hit. Cl. G10 1/00 having the Same nomenclature as respective time i [58] Field of Search 84/1.0l, 1.02, 1.03, 1.1, on Slow All time i i ned signals passed by any 84/117 445 octave of key switches are combined on a single octave output lead assigned to that octave, and signals [56] References C'ted on octave output leads are selectively combined by ITED ST S PATENTS coupler logic, output signals derivable from the cou- 3,594,487 7 1971 Jones, Jr. 84/l.l p logic tw rk ng m n d with pulse position 3,610,799 10/1971 Watson 84/ 1.01 signals derived directly from the source to provide co- 3,6l0,800 0/ 97 ut ch 8 1.0 incident gate signals which cause tone source signals 3,647,929 3/1972 Mime 34/1-01 to be fed via tone color filters 'to an output load. 3,674,907 7/1972 Derry 84/1.0l 3,683,096 8/1972 Peterson et al 8 1/103 x 6 Claims, 6 Drawin Figures 12 7 1 KEY 5 KEY sumcH E SLUHCHES MULTIPLEXER 5 Ha 12a 3 1 p 11111111;- PULSE ,gggjg cnuouza LOGlC. og s r ogi KEY sumcu i: DEMULTlPLEXER I AUDID TONE GATES GENERRTDRS TONE CDLDR FILTERS ands AB SLUI'TCHlNG U.S. Patent KEY I sumcHEs' COUPLER SUJFTCHES Nov. 4, 1975 Sheet 1 of 5 3,916,750

[23 5 KEY sumcH MULTIPLEXER 5 Ha \2a. Mumm PULSE COUPLER LDCflC. p o sng ngx 1 KEY SUMTCH E DEMULTWLEXER 5 K18 AUDlD TONE GATES eemmmnrzs TONE CDLDR F|LTERS and; TAB smrrcume U.S. Patent Nov. 4, 1975 Sheet 4 of5 3,916,750

U.S. Patent Nov.4, 1975 Sheet5 0f5 3,916,750

229m 522 swiismv Dmja ou Jdz m .Illllllll ELECTRONIC ORGAN EMPLOYING TIME POSITION MULTIPLEXED SIGNALS CROSS-REFERENCE TO A RELATED APPLICATION This application is a division of application Ser. No. 223,629, filed Feb. 4, i972, and now US. Pat. No. 3,746,773.

BACKGROUND Many prior art electronic organs have employed key switches, which control gates which serve to transfer tone signal from tone signal sources to an amplifier and loudspeaker. A lead is provided for each note of the organ, and since leads must be provided for connecting the tone sources of the organ to the gates, and the outputs of the gates to tone signal collection buses, an

enormous footage of wire is employed in each organ, and a large number of soldered connections.

Any organ of some degree of sophistication requires octave couplers, which are essentially networks for causing to sound notes an octave above or below that called for by a given key, or notes otherwise related tonally to the called for note may be required to sound in place of the called for note.

It is an object of the present invention to transmit signals indicative of the fact that key switches are closed on a time division multiplex basis, in order to eliminate most of the wire leads of an organ, and thereby reduce its cost and complexity. Any system of multiplexing which is utilized in a sophisticated electronic organ must have provision for octave coupling. In accordance with the present invention twelve time positioned pulses are generated, each time position being allocated to a note nomenclature, and each separate octave of keys of the organ transmitting via a separate octave lead, the time positioned pulses which indicate which key nomenclatures are played within that ctave.

It follows that for a 61 note keyboard, which is usual, six octave leads are required, each carrying one or more of 12 time positioned pulses representing the 12 semitones of that octave, and that provision must be made for the 61st note. The fact that all notes of a given nomenclature are represented by the same time slot of the time division multiplexed signals provides a practical opportunity for octave coupling, by transfer of timed pulses from one octave lead to another.

SUMMARY A time division multiplex system for controlling the tone signal gates of an electronic organ, wherein to each octave of notes of the organ is allocated one lead, over which the twelve notes of that octave are transmitted as time position multiplexed note pulses, thereby reducing wiring costs in production of an organ, and transferring note pulses from one octave lead to another in order to achieve octave coupling.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a signal flow diagram of a system broadly according to the invention;

FIGS. 2a and 2b together comprise a circuit diagram, largely schematic of an organ including the features of FIG. I;

FIG. 3 is a block diagram of a pulse position source which applies time modulated signals to the multiplexer of FIGS. 1 2;

FIG. 4 is a circuit diagram illustrating an octave of keying circuits; and

FIG. 5 is a schematic circuit diagram of demultiplex gates employed in the system of FIGS. 1 3, inclusive DETAILED DESCRIPTION Referring to FIG. 1 of the accompanying drawings, 11 is a source of sequential pulses, for example a clock driven counter, which provides pulses on 12 output leads lla, each lead being connected to one stage of the counter, so that the pulses on the spatial array of leads 11 occur on a time division basis, each lead having its own time slot. The leads lla proceed to a multiplexer 12, which selects the pulses of each group of 12 according to which key of an octave of keys is actuated and steers it to an output lead 12a, on a per octave basis, so that signals on any lead 12a can have any one of 12 positions representing note nomenclatures, the lead itself being identified with a specific octave.

The signals fed to multiplexer 12 from source 11 are selectively fed through the multiplexer in response to activation by the organist of key switches 14. In a typical organ, having an upper and lower manual and a set of foot pedals, 154 key switches are provided. Each of the upper or swell manual and lower or grand manual includes five octaves of keys, each of which includes 12 semi-tones, in addition to a key for C of the octave immediately above or below the lowest or highest full octave. Key switches, in one embodiment of the invention, are provided for two full l2 semi-tone) pedal octaves, plus eight semi-tones for the octave adjacent the highest pedal full octave.

Key switches 14 are connected to multiplexer 12 in such a manner as to gate all of the notes for a particular octave in each manual to a different output lead of the multiplexer. Therefore, for the exemplary situation presented supra multiplexer 12 includes 15 output leads 12a on which are selectively derived pulse position signals in accordance with activation of the key switches 14.

The fiften output leads of multiplexer 12 are fed to coupler logic network 15 which is also responsive to settings of coupler switches 16 made by the organist. Coupler switches 16 control interconnections between the 15 output leads of multiplexer 12 so that signals from different octaves can be coupled together. Coupler logic network 15 includes a relatively small number of output leads, one for each octave of each manual of the organ. In a typical organ, of the type described, there are 19 output leads of coupler logic network 15, one for each of the 15 output leads of multiplexer 12, one for the pedal super coupled octave, one for the lower manual super coupled octave, one for the upper manual super coupled octave, and one for the upper manual subcoupled octave. On each of the 19 output leads of coupler logic network 15, there are selectively derived 12 pulse position signals indicative of the 12 semi-tones in each octave.

The output signals of coupler logic network 15 are combined with the pulse position signals derived from source 11 in decoder or demultiplexer l3. Decoder 13 includes one coincidence gate for each tone of each of the 19 octave outputs of 15. The coincidence gates are arranged by octaves so that all of the gates of one octave are responsive to the output lead of coupler logic network 15 which is designated for that octave. Within each octave,a coincidence gate is provided for each semi-tone. Like semi-tone coincidence gates of the several octaves aredriven in parallel by the same pulse position output signal of source 11, whereby at any time all of the gates having the same semi-tone nomenclature'are enabled by an output signal of source 11. In response to time coincidence between the signal supplied to eachgate of decoder 13 by source 11 and coupler logic network 15, a control signal is generated to enable a selected one of gates 17.

Oneor more of gates 17 is provided for each of the organ tones. Gates 17 include circuitry for converting (fil te ring) the relatively high frequency coincidence outputs of decoder 13 into d.c. gating voltages for controlling the passage of signals from generators 18 to the output of the gates. Signals from generators 18 are passed because the length of time a key is depressed relative to the frequency of pulses derived from source 11 is such thatat least several hundred pulses are derived from decoder 13 for each activation of one of key switches 14. Each D.C. gating voltage controls a multiplic it'y of audio gates of 17, one for each footage to be tone colored. A typical manual would have 16, 8', 4',

12% and available. Thus audio signals would be QgatBd'frOmoneDC. gating voltage. ,QThe signals derived from gates 17 are fed to conventional output circuitry including tone color filters and a tab switching network 19. Network 19 drives amplifier 20, which in turn feeds loudspeaker 21.

Reference isnow made to FIGS. 2a and 2b of the drawings wherein is illustrated a block diagram of a portion of the circuitry associated with deriving the control signals for the swell output. In FIG. 2a, shift register 31 is illustrated as including 12 different output ,l eads 12 1 132. One of leads 121 132 is provided for Leach of the semi-tones of an octave. The pulse position signals derived on leads 121 132 occur in timed se- .quence so that there is no overlap between any of the pulses and each has its own individual time slot that is unique tothe time slot of all of the other pulses. To prevent the possibility of overlap between the pulses derived on leads 121 132 shift register 31 includes circuitrywhe'reby ,the duty cycle of the pulse derived on each oftheleads is approximately per cent less than one part in 12. The pulses derived on leads 121 132 areassigned the l2 semi-tone note designations in ac- L cordance with:

TABILEI Lead No.

121 122 I23 I24 I25 I26 I27 I28 I29 I30 131 132 Designation The multiplexing pulses sequentially derived on leads switches for the upper manual are respectively indicated by reference numerals 141-145, while the switches for the lower manual key switches 36 and the pedal switches 37 are respectively indicated by

reference numerals

146 and 147. To facilitate the description, separate leads to the different octaves of the lower manual and pedal switches or multiplexers are not illustrated.

The 12 signals applied to each octave of key switches are combined on a single output lead. Thereby, the signals derived on the output leads of each of the key switches has a time position indicative of the activated or depressed key in the octave. If more than one key in a particular octave is depressed, a plurality of time position pulses are derived at the output of each of the key switches, at times dependent upon the nomenclature of the depressed key. Since a key is invariably depressed for a time interval approaching or exceeding a significant portion of a second, a large number of pulses having the same relative time position is derived for each key activation.

In addition to the five octaves of key switches included in the upper and lower manuals, these manuals include a further key switch, indicated by reference numeral 148a for the upper manual, to provide the 61 keys in each manual. Key switch 148a and the corresponding key switch for the lower manual are connected to output lead 121 of shift register 31 so that a high C note can be derived. The high C note has the same time position as the C notes derived for the other octaves.

The five octaves of signals derived from key switches for multiplexer 146 are derived onleads 151-155. The single lead for the partial octave (for the note C) on the lower manual is derived on lead 156.

The two full octaves of notes derived from pedal switches of multiplexer 147, are derived on

leads

161 and 162, while the partial, eight-note octave is derived on lead 163.

Consideration will now be given to the specific circuitry in

coupler logic networks

41, 42 and 43. Coupler logic network 41 includes l8 selectively energized inverting amplifiers 171-188. Amplifiers 171-188 are arranged in three sets of six, whereby power is supplied to the six amplifiers of each set simultaneously. If no power is supplied to the amplifiers of a particular set, the amplifiers can be considered as open circuited switches. In response to power being supplied to the amplifiers, they function as unity gain, inverting amplifiers and can be considered as closed circuited switches. Power is supplied to amplifiers 171-188 through three normally open circuited coupler tab switches 191-193. In response to the organist closing any of the coupler tab switches 191-193 power is supplied to a selected six of the inverting amplifiers to activate them into a closed state. Amplifiers 171-188 are connected to be responsive to closure of coupler tab switches 191-193 so that there is coupling to the next adjacent higher footage octave of each of the octaves associated with switches 141-145 and 148 in response to closure of switch 191. There is coupling to the same octave in response to closure of switch 192, while there is coupling to the next adjacent lower footage octave in response to closure of switch 193. To these ends, power is supplied to amplifiers 171- 176 in response to closure of switch .191; power is supplied to amplifiers 177-182 in response to closure of switch 192; and

closure of switch 193. A convenient packaging arrangement for the amplifi- The outputs of amplifiers for similarly designated ocers included in coupling matrices 41-43 involves the taves of coupler logic network 41 are connected to like use of multiple integrated circuit inverting amplifiers, output signals, in accordance with: each mounted on a single integrated chip and having a TABLE II 7' Output Octave 0. l 2 3 4 5 6 7 Am lifier 183(3a) l77(2a) mus 7 I72( la) 173 (la) 174(la), 175(la) 176(18) Amplifier I l84( 3a) 178(2a) 179(2a) 180(2a) l8l(2a) 182(2a) Amplifier 185(3a) 186(321) 187(3a) 188(3a) In Table II, the numbers in parenthesis indicate the common power supply terminal. One particular, presunit order values for the activated coupler tab switches, ently available integrated circuit chip includes six amthe numbers running in ascending order from O to 7 inplifiers thereby rendering it particularly adapted for use dicate the eight output octaves of coupler logic netin conjunction with the present invention. These ampliwork 41, and the three digit numbers indicate the referfiers have open collector outputs allowing them to sink ence numerals for the amplifiers. Hence, e.g., Table 11 current to the negative supply only if they are energized indicates that in response to coupler tab switch 193 from the coupler tab and turned on from the time mulbeing closed, the output signals derived from key tiplexed key switch input. These open collector outputs switches 141-145 are fed to the output leads for the occan then be wired OR without using additional logic taves from O to 5 via amplifiers 183-188. gates.

Coupler logic network 42 includes 12 amplifiers Demultiplexer or decoder 13, FIG. 1, is illustrated in 201-212 arranged similarly to the coupling amplifiers FIG. 2a as including seven sets of AND gates (coinciof logic network 41. Inverting amplifiers 201-212 are dence gates) 251 257. Each set of AND gates 251 responsive to two additional coupler tab switches 257 includes 12 individual AND gates, one for each of 221-222 which energize the amplifiers so that they sethe semi-tones of a complete octave. AND gate sets lectively operate as open and closed circuited switches. 251 257 are respectively responsive to the output sig- Output leads of amplifiers 201-212 are connected to nals derived for the seven lowest octaves (0,1,2, 3,4,5

A output leads corresponding with those of amplifiers and 6) derived by combining the outputs of coupler 171-182. The particular connections between these logic networks 41 43. The individual gates within amplifiers and the output leads are given by: each set of AND gates 251 257 are responsive to the TABLE 111 Output Octaves l 2 3 4 5 6 7 Am lifier 207(2b) 20l( lb) 202(lh) 203(lb) 204(lb) 205(1b) 2()6( lb) Amplifier v 208(2b) 209(2b) 210(2b) 211(2b) 212(2b) In Table III, the numbers in parenflhesis indicate which amplifiers are responsive to coupler tab switches 221 -222, whereby those amplifiers responsive to switch 221 are indicated by (lb) and those responsive to switch 222 are indicated by (2b).

Couplerlogic network 43 includes six selectively energized inverting amplifiers 231-236, arranged in two sets of three. Power is selectively applied to the two sets of amplifiers in response to closure of coupler tab switches 241-242.

Amplifiers

231, 232 and 233 provide coupling to the higher footage outputs, and amplifiers 234-236 provide coupling to the outputs at the same footages as coupled through switches 147 to leads 161-163. Connections between the output leads of amplifiers 231-236 and control of the amplifiers in response to activation of the selected ones of coupler tab switches 241-242 is in accordance with:

12 pulse position signals derived on leads 121 132, as coupled through driver amplifiers 261. The AND gates in each of sets 251 257 respond to the signals fed thereto from driver amplifiers 261 and the combined output leads of

coupler logic networks

41, 42 and 43 to derive d.c. gating signals that enable audio tones from tone generators 91 97 to be selectively passed through the sets of audio gates 281 287 to network 19, FIG. 1.

In addition to the seven sets of 12 AND gates, a further AND gate 271 is provided. AND gate 271 is responsive to the octave number 7 output derived by combining the signals of coupler logic networks 41 43 and the Cnote output signal by shift register 31 on lead 121. AND gate 271 responds to coincidence between the octave number 7 input thereof and the signal on TABLE IV lead 121 to derive an enable signal that gates the output Output Octave of tone generator 98 through audio gate 288 to circuit 1 2 3 4 19. Amplifier 23400 Blue) 232( m 233 1c) Reference is now made to FIG. of the drawing Amplifier 235( 2c) 236(2c) wherein there is illustrated an embodiment for an oscillator and shift register that derives the pulse position or 12 phase signal. Basically, the 12 phase source includes In Table IV, the numbers in parenthesis designate a free running transistorized multivibrator 301 which which of coupler tab switches 241-242 is depressed, drives a plurality of cascaded bistable flip-flops, that in whereby (1c) designates activation of coupler switch turn drive a logic network 300 having 12 output leads 241 and (2c) designates coupler switch 242. for deriving the 12 phase or pulse position signal.

Transistorized multivibrator 301 is of conventional design and derives a square wave voltage at terminal 302, with a frequency, for example, of 240 KHz. The

square wave voltage developed at terminal 302 is shaped into a series of positive and negative pulses, one of which is derived in response to each transition of the square wave by differentiator 303. The negative going pulses derived by differentiator 303 are amplified by driver 304 which feeds toggle flip-flop 305 in parallel with input terminals of AND

gates

306 and 307. Flipflop 305 includes a true output terminal (O) which drives the other input terminal of AND gate 306 in parallel with clock input terminals (C) of J K flip-flops 308 310.

Flip-flops 308 310 are cascaded with each other so that they, in effect, form a three-stage counter, having a maximum count of eight. Connections between flipflops 308-310 enable them to function as a divide-bysix ring'counter responsive to the voltage developed at the Q output terminal of flip-flop 305. Because of the toggle action of flip-flop 305, the flip-flops 305 and 308-310 effectively form a divide-by-12 counter, or frequency divider for'the 240 KHz output of multivibrator 301. To provide feedback required to establish the divide-by-six count fromthe counter including flipflops 308-.310, AND gate 311 is provided. AND gate 311 includes input terminals responsive to signals developed at true output terminals (C) and (D) of flipflops 309-310 and develops an output signal that is supplied to the K input terminal of flip-flop 308, the J input terminal of which is responsive to the completively) of flip-flop 305 and the output of driver 304, in-

cludes l2 three-input NAND gates 32l332. Threeinput NAND gates 321-332 respond to the output signals of

gates

306 and 307 and signals developed at the true and complementary output terminals of flip-flops 308-310 to'derive a 12 phase, pulse position signal, in such a manner that each pulse has a duty cycle of approximately lO percent less than one part in 12. The signal derived at the output terminal of each NAND gate is in a nonoverlapping time position relative to the signal derived at each of the other NAND gates, and each of the signals is equispaced from adjacent signals.

The connections between

gates

306 and 307 and the output terminals of flip-flops 308-310 and input terminals of NAND gates 321-332 are given by:

8} i TABLE V-continued I VI'NPUT SIGNALS ACD NAND GATE In Table V, the outputs of gates306 and 307 are respectively denominated as A and A; the signals derived responsive to a pulsating output of one of gates 306 and I 307, as indicated in Table V by the inclusion of an A or A input signal to each of the NAND gates.

Reference is now made to FIG. 4 of the drawings wherein is illustrated a preferred embodiment of a typical octave of key switches, such as the first octave 41 of upper manual key switches 35. The octave of key switches includes 12input leads, one for each semitone of an octave and each responsive to a different one of the signals on leads 121-132, asderived from NAND gates 321-332. Each of leads 341-352 is connected through a separate key switch 361-372 to the input terminal'of inverting amplifier 373. One'of the key switches 361-372 is provided for each of the keys of the octave being considered. Only one switch is provided for each of the keys, regardless of the tab coupling which might be desired for a particular key be cause of the inclusion of matrices 41-43. To prevent sneak .currents, each of key switches 361-372 is connected in series with a different one of diodes 374, biased in such a manner as to pass the negative going multiplexing signals supplied to leads 341-352 by NAND gates 321-332. Because the multiplexing signals are supplied to leads 341-352 in different time positions, the waveform developed on the single output lead of amplifier 373, which is responsive to signals supplied to all of leads .341-352, is, in effect, time position modulated by the depression of key switches 361-372. t

In FIG. 5 of the drawings is illustrated a portion of the circuitry included within one of the groups of l2 AND gates, such as group or set 257 ofAND gates. in FIG. 5, complete circuitry is given for the C gate included in group 257, while fragmentary circuitry is given for the B gate. 1

TheC gate includes NPNtransistor 391, having a base electrode responsive to a positive going multiplexing pulse derived by the driver inverting amplifier 261, responsive to the signal on lead 121, while the B gate comprises NPN transistor 392 having a base electrode responsiveto the multiplexing pulse derived by the driver, inverting amplifier 261 responsive to the signal on lead 132. The emitters of

transistors

391 and 392 have a c'ommo n connection to .1000, ohm resistor 393 that is responsive to a negative going pulse derived by the Number 6 output lead of a matrix comprising networks 41-43. The emitter collector path of transistor 391 is biased to a conducting state with a duty cycle of ten percent lessthan one part in 12, the same duty cycle as the multiplexing pulses, in response to the positive and negative multiplexing pulses applied to its base and emitter electrodes. The 20 KHZ, low duty cycle activation of the emitter collector path of transistor 391' is converted into a dc. gating potential for tone generator sources connected to

terminals

394 and 395 by connecting a relatively large, 0.33 microfarad capacitor 396 between the collector of transistor 391 and ground. Capacitor 396 serves as a bias for slow attack and fast attack gating circuits for the tone signals supplied to

terminals

394 and 395.

The slow attack circuit for the tone supplied to tenninal 394 includes a resistive voltage divider comprising two 100

kilohm resistors

397 and 398, the junction of which is connected to the cathode of diode 399, having an anode that is biased through resistor 401. The tone source at terminal 394 is connected to the other terminal of resistor 398 and is selectively coupled through diode 399 to tone color circuits 319. The tone signal supplied to tenninal 394 is a square wave voltage having variations between 15 volts and +23 volts, voltages which enable selective coupling through the anode cathode path of biased diode 399.

If there is no time coincidence between the positive and negative pulses supplied to the base and emitter of transistor 391, the square wave voltage at terminal 394 alternately charges and discharges capacitor 396 between a pair of voltage levels, both of which are sufficiently high to maintain diode 399 in a back biased condition. In response to transistor 391 being forward biased at 20 KHz rate with a low duty cycle of approximately one part in 12, the charge on capacitor 396 is reduced, with a resulting decrease in the voltage across the capacitor electrodes. In response to the reduced voltage across the electrodes of capacitor 396, the dc. voltage level at the cathode of diode 399 is reduced sufficiently to enable the square wave tone signal at tenninal 394 to be passed through diode 399 to tone color circuit 319.

To provide fast attack in response to activation of transistor 391 into a conducting state, the tone signal at terminal 395 is selectively coupled to the collector of transistor 391 via

resistors

402 and 403, which are connected in series with the parallel combination of resistor 404 and capacitor 405. A junction between

resistors

402 and 403 is connected to the cathode of diode 406, the anode of which is connected to a +1 5 volt d.c. biasing source at terminal 407 via resistor 408. The voltage of the tone source connected to terminal 395 has a different frequency than the tone source connected to terminal 394 but varies between volts and +23 volts so that diode 406 functions in a similar manner to diode 399. The time required for the source connected to terminal 395 to be coupled through diode 406 is considerably less than that required for the source connected to terminal 394 to be coupled through diode 399 because of the inclusion of capacitor 405 in the circuit between terminal 395 and the collector of transistor 391. Typically, the time constant of the fast attack circuit is milliseconds, a result achieved by selecting the values of

resistors

403 and 404 to be 47 kilohms, the resistance of resistor 402 to be 100 kilohms, and the value of capacitance 405 to be 0.33 microfarads.

In general more than one audio gate would be connected to the slow and fast attack bias. Only one each are shown for simplicity. For example, if three sets of gates are connected to the collector of transistor 391 .10 andthree sets ofgates are connected to terminal 409,

capacitors

396 and 405 would beincreased to one microfarad and

resistors

393 and 404 would be reduced to 330ohms and l5 kilohms respectively. This scaling would'maintain the same time constant or attack rate as in the exemplary case.

In this general case, generator tones at 16', 8, 4', 2 2', and 1 can be keyed on responsive to

coupler gates

175, 182, 205 and 212. The lower footages (l6, 8 and 4) on the slow attack and the higher footages (2 2', and l) on the fast attack.

It is to be understood that similar circuits are connected in the collector circuit of transistor 392 and are selectively activated in response to simultaneous application of positive and negative multiplexing pulses to the base and emitter thereof. Simultaneous application of the multiplexing pulses to the base and emitter of transistor 392 results in passing B tones from tone generator sources connected in fast and slow attack circuits in the collector thereof in the manner described with regard to the slow and fast attack circuits of transistor 391.

What is claimed is:

1. In a multiplex organ system, a key switch for each note of a multi-octave manual, means for converting actuated ones of the keys of each octave of said manual separately into only 12 pulse codings in concurrent octaval note frames which occur in common for the separate octaves, and means for converting the codings of said pulses to tones of said organ.

2. The combination according to claim 1, wherein is included means for converting the codings of pulses in one note frame pertaining to one octave of said organ to tones of a different octave of said organ.

3. An electronic multi-octave organ, comprising a multi-octave array of key switches, a source of 12 coded pulses, each of said pulses occupying a predetermined time slot corresponding with a note nomenclature on a time division multiplex basis, a plurality of channels corresponding respectively with different octaves of said organ, means responsive to selective actuations of said key switches for selecting said coded pulses for transmission in said channels, an array of tone signal sources, a load, and means responsive to the pulses selected for transmission in said channels for concurrently applying to said load tone signals corresponding selectively with different footages of said organ. I

4. An electric organ, comprising an array of key switches, a source of 12 sequential pulses each occupying a predetermined time slot on a time division multiplex basis and each time slot corresponding with all keys of a given nomenclature, a plurality of leads each corresponding with a different octave of keys of said organ, means responsive to selective actuation of said key switches for selecting said pulses for transmission on said leads to convey the selected pulses according to the octave of each actuated key and its note nomenclature, an array of tone signal sources, a load circuit, and means responsive to said pulses for applying to said load circuit tone signals of pitch according to the time positions of said pulses and the leads on which said pulses occur.

5. The combination according to claim 4, wherein is included means for transferring pulses from one of said channels to another one of said channels at will.

6. In an electronic organ having plural octaves of keys, means for converting notes of a first octave of 12 said second octave, a sequence of tone signal sources. and means for selectively applying said groups of pulses to control said tone signal sources to provide tone signals corresponding with said actuated ones of said keys. l

Claims

3. An electronic multi-octave organ, comprising a multi-octave array of key switches, a source of 12 coded pulses, each of said pulses occupying a predetermined time slot corresponding with a note nomenclature on a time division multiplex basis, a plurality of channels corresponding respectively with different octaves of said organ, means responsive to selective actuations of said key switches for selecting said coded pulses for transmission in said channels, an array of tone signal sources, a load, and means responsive to the pulses selected for transmission in said channels for concurrently applying to said load tone signals corresponding selectively with different footages of said organ.

6. In an electronic organ having plural octaves of keys, means for converting notes of a first octave of said organ into time positions of first pulses occupying those of 12 time positions corresponding with actuated ones of the keys of said first octave, means for converting notes of a second octave of said organ into time positions of further pulses occupying those of said 12 time positions corresponding with actuated ones of keys of said second octave, a sequence of tone signal sources, and means for selectively applying said groups of pulses to control said tone signal sources to provide tone signals corresponding with said actuated ones of said keys.