US3565995A

US3565995A - Electronic organ employing automatic coupling of solo and accompaniment notes

Info

Publication number: US3565995A
Application number: US768321A
Authority: US
Inventors: David A Bunger
Original assignee: DH Baldwin Co
Current assignee: BPO ACQUISITION CORP; Baldwin Piano and Organ Co; DH Baldwin Co
Priority date: 1968-10-17
Filing date: 1968-10-17
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

An array of tone signal sources is controlled by solo keys and by accompaniment keys for transfer respectively to solo tonecolor filters and accompaniment filters, and thence to a loud speaker, in the manner usual in electronic organs. Tones collected in response to actuation of accompaniment keys are also applied to the input of a normally inhibited gate having its output connected to solo filters. Actuation of any one or more of the solo keys uninhibits the gate, selectively either transiently or for the duration of the actuation, by generating appropriate gate control pulses. A second normally inhibited gate is paralleled to the first gate, and similarly controlled, but its input circuit is a further gate which is supplied with reiteration voltage.

Description

United States atent 13,565,995

[72] Inventor David A. Bunger 3,040,612 5/1962 Dorf 84/1 1 7 Cincinnati, Ohio 3,109,341 11/1963 Gibbs 84/1.01X [21] Appl. No. 768,321 3,223,768 12/1965 Munch et al..... 84/1.01 [22] Filed Oct. 17,1968 3,461,217 8/1969 Omura et a1. 84/1.08 [45] Patented Feb. 23, 1971 Prima [73] Asslgnee gis i rgg g g Assistant Examiner-Stanley J. Witkowski AttorneysW. ll. Breunig, D. H. Baldwin Co. and Hurvitz,

Rose & Greene [54] ELECTRONIC ORGAN EMPLOYING AUTOMATIC COUPLING OF SOLO AND ACCOMPANIMENT NOTES ABSTRACT: An array of tone signal sources is controlled by 21 Claims 2 Drawing Figs solo keys and by accompaniment keys for transfer respectively to solo tone-color filters and accompaniment filters, and U-S- then e t a l ud eaker in the manner usual in electronic or. f Cl i Gloh 1/00 gans. Tones collected in response to actuation of accompaniment keys are also to the input of a normally 1-08; 84/1-01, 11911150) gate having its output connected to solo filters. Actuation of 56] References Cited any one or more of the solo keys uninhibits the gate, selectively either transiently or for the duration of the actuation, by

UNITED STATES PATENTS generating appropriate gate control pulses. 3,247,310 4/1966 Stinson 84/ 1.17 A second normally inhibited gate is paralleled to the first 3,283,056 11/1966 Cookerly et a1. 84/ 1.01 gate, and similarly controlled, but its input circuit is a further 2,988,945 5/1961 Osborne et a1 84/1.01 gate which is supplied with reiteration voltage.

PATENTEU FEB23 l97| C 68:? INVENTOR DAVID auueen s'r an SIN .5320 gas; @985 58.5 A

m ii.

In -LIJ ATTORNEY 5 the solo note.

between circuit and gate 32.

BACKGROUND or Tl-lE INVENTION Conventional coupler systems for electronic organs cause signals keyed from one keyboard, for example, to pass through the tone-color circuits of another keyboard, whether or not notes are played on the other keyboard. U.S. Pat. Nos. 3,247,3l to Stinson and 3,283,056 to Cookerly et al., by means of elaborate and expensive keying systems, teach causing notes played on an accompaniment manual to be heard through solo filters only when a solo note is played, but in the octave immediately below the solonote. The present invention removes the recited limitation and simplifies the patented systems.

The present invention provides a relatively simple system for causing notes played on an accompaniment keyboard to be heard through solo filters at the same,or harmonically related, pitches as the notes played on the accompaniment manual, only when a solo note is played, but'regardless of the pitch of SUMMARY OF THE INVENTION A trigger pulse, derived from a direct current circuit keyed concurrently with a signal key switch is in a solo keyboard is shaped and used to turn on a PET gate between an accompaniment key switch and a solo tone-color circuit, so that BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram of a preferred embodiment of the invention.

FIG. 2 is a circuit diagram of the system of FIG. 1.

DESCRIPTION OF THE PREFERREIIl EMBODIMENT In FIG. 1, sources 1 and 3 of musical signals f, and respectively, are shown connected via key switches 5 and 7, respectively, activated by keys (not shown) in difi'erent keyboards, tone-color filters TC, and TC,,, respectively, and

stop switches

9 and 11, respectively, to arr-output system composed of an amplifier 13 and loudspeaker 15. Source 1 has also a path to the output system via a percussion gate 17, tone-color filter PERC and stop switch 19. In addition, a source of direct current voltage v.-is connected via a trigger and pulse-shaping circuit 21 and a normally inhibited gate 23 to the input side of tone-color filter TC,. There is also a path from nigger and pulse-shaping circuit 21 via an auxiliary key switch 25 (ganged to switch 5) to gate 17. The output side of switch 7 is also connected to gate 23, as shown. A switch 27 is In operation, closure of key switch Sdirects a signal from tone source 1 directly via filter TC,, for coloring thereby, and via switch 9 (if closed) to the amplifier 13 and loudspeaker 15 for conversion to. sound. Concurrently, switch 25 is closed and direct current voltage v. uninhibits gate 17. If tab switch 19 is closed, signal will pass from source 1 through gate 17 for coloring by tone-color filter PERC and conversion to sound in the loudspeaker 15. If switch 7 (in anotherkeyboard or in the accompaniment section of a split keyboard) is closed, signal at frequency f, will pass for coloring byjTC, and for conversion to sound in loudspeaker 15, if tab switch 11 is closed. However, closure of switch 25 generates a pulse in circuit 21, which is there shaped, and it switch 27 is closed uninhibits gate 23, whereupon signal can also pass from source 3 via gate 23 to tone-color filter TC,, for conversion to sound, if switch 9 is closed. Thus are illustrated in FIG; lithe basic essential elements of an automatic coupling system wherein a keyed signal in one keyboard will be heard through a filter in another keyboard, only if and when a note is played on the other keyboard.

Sources

2, 4, 6 and 8 of FIG. 2 represent four of a gamut preferably of frequency-dividing flip-flop tone sources, as known in the art, and they generate tone signals corresponding to notes C B C and 15,, respectively, of the equally-tempered scale. Source 8 is connected via key switch 10, operable concurrently with key switches 12 and l4 by a key 16 of a solo keyboard 18, represented by dashed lines.

Switches

10 and 12 are preferably of the variable-resistance type disclosed in U.S. Pat. No. 3,206,701 to Gregory, the latter switch being connected to a source E of tone signal.

Switches

10 and 12 are respectively connected to a suitable tone-color filters 8'TC and 4'TC, which, in turn are connectable by stop-

tab switches

20 and 22, respectively, to a collector 24, thence to a suitable amplifier 26 and loudspeaker system 28. The switch 14 may be of a direct-contact type and is shown connected between a percussion gate 30 and a terminal 32 from a negative source (not shown) of direct current via two

series resistors

34 and 36. The percussion gate 30 may be of a suitable type known in the art, providing a sharp rise and gradual decay of tone signal passing therethrough from the source 8 to a suitable filter PERC in response to application of DC gating voltage. The filter PERC may be connected to the amplifier 26 and loudspeaker 28 via a tab switch 38,

Branches

40, 42 and 44 indicate that signals from other key switches actuated from keyboard 18 may be connected to the tone-color filters according to usual practice.

Connected to the junction 128 of

resistances

34 and 36 is one tenninal of capacitor 48, the remaining terminal being connected directly to the base of transistor T,. The emitter of T, is connected directly to terminal 32, and a resistance 50 is connected from base to emitter of T,. The emitter of T, is also connected to ground via series resistances 58 and 60, and its collector is connected to ground via series resistances 54, 56. The collector is thus positive with respect to the emitter which is maintained at 100 v. below ground.

T, is normally nonconductive, but on closure of switch 14, current is drawn .in at the gating terminal :of percussive gate 30, and a voltage is developed across resistor 36, which is transferred as a transient pulse to the base of T,, and renders the latter conductive transiently. If switch 52 is closed, however, the capacitor 48 is short circuited and a steady state conductivity for the duration of closure of switch 14 is effected.

The junction of collector load resistances 54, 56 is directly connected to the base of NPN transistor T,, the emitter of which is connected back to ground in the junction of resistances 58, 60. The collector of T, is connected to ground via load resistance 66. T, is therefore normally conductive so long as T, is nonconductive.

The voltage at the emitter of T, is -12. The emitter of T, is connected via a large resistance 64. to a stationary switch contact 61 of a switch 62. The collectorof T, is connected via series resistances 68, 70,to a second stationary switch contact 61a. The resistances 68, 70, are shuntedby a diode 72 having its anode connected to the collector of T,, and which is therefore nonconductive of transistor current. Between the movable contact of switch 62 and ground is connected a capacitor 71, and the movable contact is also connected to the gate terminal G of a field efiect transistor (FET) T whose drain terminal D is connected via a coupling capacitor 74 to filter 4'TC. A shunt resistor 76 is connected between terminal D of FET T and a common return path ground. The source terminal S of T, has one path via a-resistor 78 to ground and another via coupling capacitor 80 and series resistor 82 to path 84. The last-mentioned group of components comprise a gate 73, the operation of which will be discussed hereinafter.

The path 84 serves to connect tone source 8 via variable-resistance key switch 86 (operable by key'88 of an accompaniment keyboard 90) to an accompaniment tone-color filter 4'TCA. Tab switch 92 connects, at will, this filter with amplifi 94, actuated concurrently with switch 86, connects tone source 4 to a second accompaniment filter 8'TCA, with tab switch 96 connecting, at will, thisfilterto amplifier 26 and loudspeaker 28. A second key 98 of the keyboard 90 may ac tuate variable-

resistance key switches

100 and 102 to connect tone sources 6 and 2, respectively, via

collectors

104 and 106, respectively to filters 4'TCA and 8'TCA, respectively.

An alternate path fromcollector 106 to the output system (amplifier 26 and loudspeaker 28) exists via a resistor 108, a coupling capacitor 110, a PET T,, a second gate 112 (which may be similar to gate 73) and a filter 8'TC. The FET T and its associated normal components, including a shunt resistor 114 connected from source to ground, comprises a reiteration gate, the gate terminal G of T, being connected to a reiteration oscillator 116 via a switch 117 and a filter network 118. The network 118 is composed of resistors and capacitors, as shown, and serves to filter high frequencies from the oscillator output. The oscillator 116 comprises a-rnultivibrator of substantially conventional character,

diodes

120 and 122 and capacitor 124 sewing not only to assure the starting of oscillations but also to delay them slightly. A potentiometer 126 provides control of the reiteration rate of the oscillator.

In operation, assuming that a chord composed of notes C and E is held on the accompaniment keyboard by depressing 1 keys 88 and 98, tone signals pass from

sources

2, 4, 6 and 8 through

key switches

102, 100, 94 and. 86, respectively, via

collectors

104 and 106 to the output system via either filter 4'TCA or 8TCA or both depending on which of

switches

92 and 96 is closed. Obviously, if

switches

92 and 96 are open, no signals will be heard in the output system. However, if a note E, (which, of course, would hannonize with C, and E were played on the solo manual by depressing key 16, it would be heard in the output system if tab switch 20 were also closed,

the signal passing via switch 10 as filtered by 8'TC. B, would also be heard, via key switch 12, if tab switch 22 were closed, as colored by T'TC. However, the concurrent closing of switch 14 causes direct current to. pass from terminal 32 through

resistors

36 and 34, thru raising the potential of junction 128. Assuming first that switch 52 is closed (for continuous operation of the trigger and pulse-shaping circuit 46) and switch 62 is in the upper position, the DC level of the base of transistor T,, which is normally nonconductive, is raised with respect to the emitter and T, conducts. Conduction in T, causes the base of T which is normally conductive to go negative,'thus cutting T, off. Then capacitor 71, the upper plate of which has been charged negatively, discharges quickly via diode 72 and resistor 66, thus raising the potential of the gate terminal 6 of FET T causing it to conduct signal from the line 84 through resistor 82, capacitor 80, capacitor 74, to 4TC, thence to the output system if tab switch 22 is closed. Thesignal will be heard so long as the key 16 is held. Upon release of the key, '1, turns off, and '1, turns on again at a rate determined by the time constant of the'ca'pacitor 71 and the resistors 70 and 68, as capacitor 71 charges to a negative voltage. FET T, again becomes nonconductive, turning off the signal from source 8 via key switch 86. I v v If the switch 52 is in the pizzicato (PlZZ) position, the operation starts in the same way, but transistor T, quickly turns off as capacitor 48 charges up, and then discharges. By the tiine it discharges, via

resistors

36 and 50, T, has become nonconductive again, and the circuit "I, wait for another closing of key 16 before being operative again. If the selector switch 62 is in the lower position, the gate G of PET T, remains at -l2 v. keeping capacitor 7l charged, and '1; does not respond to operation of key 16 (or any other key in the solo manual).

Gate 112 is similar to that of gate 73 However, the reiteration gate including T being in series with gate 112, a signal Thus, accompaniment chords cannot only be coupled to a solo manual, automatically playable only when solo notes are played, but the pitch of the chords, as related to the solo notes, may be selected as desired by the operation of tone-color tab switches, such as 20 and 22. 3

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

lclaim: v

1. In an electronic organ having a gamut of tone signal sources, a first keyboard, a second keyboard, a first tone-color filter, a second tone-color filter, an output system, a first key switch operable by a key in said first keyboard and coupled between one of said sources and said output system via said first tone-color filter, a second key switch operable by a key in said second keyboard and coupled between another of said sources and said output system via said second tone-color filter the combination comprising:

a direct current supply;

an auxiliary key switch ganged to said first key switch;

a trigger and pulse-shaping circuit means coupled between said auxiliary key switch and said direct current supply and responsive to closure of said auxiliary key switch for generating a control pulse; and

a normally-inhibited gate coupled to said trigger and pulseshaping circuit, and responsive to said control pulse to uninhibit said gate, said gate being also coupled between said second key switch and to said first tone-color filter, whereby actuation of said key in said first keyboard closes said auxiliary key switch creates a pulse in said trigger and pulse-shaping circuit operative to uninhibit said gate so as to cause a signal to flow between said other source and said output system via said second key switch and said first tone-color filter when said key in said second keyboard is actuated.

2. The combination according to claim 1, including:

a third tone-color filter;

a third key switch operable by said key in said first keyboard and coupled between a further one of said sources and said output system via said third tone-color filter;

a fourth tone-color filter;

a fourth key switch operable by said key in said second keyboard and coupled between one of said sources and said output system via said fourth tone-color filter; and

I a second normally-inhibited gate coupled to said trigger and pulse-shaping circuit, and responsive to said control pulse to uninhibit said gate, said second gate being coupled between said fourth key switch and said third tone-color filter, whereby actuation of said key in said first keyboard closes said auxiliary key switch,-thereby creating a pulse in said trigger and pulse-shaping circuit operative to uninhibit said second gate and to cause a signal to flow between said one of said sourcesand said output system via said fourth key switch and said third tone-color filter,

when said key in said second keyboard is actuated.

3. The combination according to claim 1, including a reiteration gate coupled between said second key switch and said second normally-inhibited gate; 1

a reiteration oscillator coupled to said reiteration gate for rendering said reiteration gate reiteratively inhibited and uninhibited; and

switch means coupled between said reiteration gate and said reiteration oscillator.

4. The combination according to claim 3 wherein said reiteration oscillator includes means for at altering the rate of oscillation thereof.

may be periodically interrupted (with switch 117 closed) by 5. The method of automatically coupling a signal derived the on-off operation of T, as controlled by the reiteration oscillator 116. The reiteration is effective as illustrated, only on an 8'voice in the solo manual. Should reiteration be desired for a 4'voice, a reiteration gate could be inserted between gate 73 and line 84.

from closing a key switch in one keyboard to a tone-color filter for another keyboard which comprises:

deriving a pulse from depression of any key in said other keyboard; Y amplifying and shaping said pulse; and

applying said pulse to uninhibit a normally inhibited gate operative between said key switch in said one keyboard and said tone-color filter. 6. In an electronic organ; a series of tone signal sources; an array of solo keys; an array of accompaniment keys; a solo tone color filter; an accompaniment tone-color filter; a loudspeaker system connected in cascade with said tonecolor filters; means responsive to actuation of selected ones of said solo keys for connecting corresponding ones of said tone signal sources to said solo tone-color filters; means responsive to actuation of selected ones of said accompaniment keys for connecting corresponding ones of said tone signal sources to said accompaniment tonecolor filter; and gate means responsive to actuation of any one or more of said solo keys for connecting tone signal sources called for only by the actuated accompaniment keys to said solo tone-color filter. 7. The combination according to claim 6, wherein said gate means is arranged and adapted to be operative while said any of said solo keys are actuated for the duration of the actuation. 8. The combination according to claim 6, wherein said gate means is arranged and adapted to be only transiently operative in response only to initial actuation of. any said solo keys regardless of the then actuated condition of other of said solo keys.

9. In an electronic organ: a series of tone signal sources; a array of solo keys; an array of accompaniment keys; a solo tone-color filter; an accompaniment tone-color filter; a loudspeaker system connected in cascade with said tonecolor filters; means responsive to actuation of selected ones of said solo keys for connecting corresponding ones of said tone signal sources to said solo tone-color filter; means responsive to actuation of selected ones of said accompaniment keys for connecting corresponding ones of said tone signal sources to. said accompaniment tonecolor filters; means responsive to actuation of any one or more of said solo keys for connecting tone signal sources corresponding only with the actuated accompaniment keys to said solo tone-color filter, wherein is provided a selective twocondition switch; and means comprising a pulse shaping circuit responsive according to the condition of said selective two-condition switch for connecting tone signal corresponding with accompaniment keys to said solo tone-color filter transiently on actuation of any of said solo keys or for the duration of actuation of said solo keys. 10. The combination according to claim 9, wherein said last means includes a normally nonconductive transistor and a normally conductive transistor connected in cascade:

means responsive to rendering said normally nonconductive transistor conductive to render said normally conductive transistor nonconductive; a gate connected between said tone sources and said solo tonecolor filter; I a means uninhibiting said gate in response to the conductive condition of said normally conductive transistor and inhibiting said gate in response to the nonconductive condition of said normally conductive transistor; and means applying to said pulse to render conductive said normally nonconductive transistor selectively on a transient and a steady state basis. 11. In an electronic organ: a source of negative voltage; a resistance connected in series with said source of voltage;

a plurality of load circuits selectively connected in cascade with said resistance;

a plurality of key switches;

means responsive to closure of any one or more of said key switches for completing a circuit from said source of voltage through said resistance to one or more of said load circuits to develop a control pulse;

a first transistor having a base, an emitter and a collector;

means connected said base to the load side of said resistance and said emitter directly to said source of voltage;

an emitter resistance connected between said emitter and a reference point;

a collector resistance connected between said collector and said reference point;

a gate inhibited by negative voltage applied to a gating electrode; and

means controlling said gate at said gating electrode selectively directly from said emitter or in response to voltage developed across at least part of said collector resistance.

12. The combination according to claim 11, wherein said gate includes:

a capacitor connected between said gating electrode and a reference point;

a terminal;

means for at will selectively connecting said capacitor to said emitter and to said terminal; and

means for discharging said capacitor in response to said control pulse developed across said resistance when said capacitor is connected to said terminal.

13. A gating circuit comprising:

a NPN transistor having a base, an emitter and a collector;

a source of negative voltage connected to said emitter;

a load resistance connected between said collector and ground; a

a load capacitor having a first electrode connected to ground and having a second electrode;

a timing resistance connected in series between said second electrode and said collector;

a diode connected across said timing resistance poled in discharge relation to said capacitor through said transistor;

means connected to said base for maintaining said transistor normally conductive;

mean means for randomly rendering said transistor nonconductive;

a gate having a control terminal, a signal input terminal and a signal output terminal;

means connecting said control terminal to said second electrode;

a source of tone signal connected to said input terminal; and

a load connected to an output circuit, said gate being of the type inhibited by negative voltage.

14. In an electronic organ:

a tone generator including a gamut of tone signal sources;

a first tone-color filter; 1

a second tone-color filter;

a loudspeaker system connected to said tone-color filters;

a first array of keys for calling forth tones in response to said tone signal sources via said first tone-color filters; and

means responsive to actuation of any of a said first array of keys for calling forth tones from said tone signal sources at pitches selected by keys of said second array of keys.

15. The combination according to claim 14, wherein said last means includes;

means for generating a control pulse in response to each actuation of any one or more of said first array of keys;

a collector for all tone signals called for by actuation of said second array of keys;

a normally inhibited gate connecting said collector with said first tone-color filter; and

means responsive to said control pulse for uninhibiting said gate.

16. The combination according to claim 15, wherein said means for uninhibiting includes means for periodically uninhibiting at a reiteration rate.

17. In an electronic organ;

a source of an array of tone signals arranged according to the equally tempered scale;

a tone-color filter;

a first normally inhibited gate;

a second normally inhibited gate;

means connecting said gates in cascade with each other between said source of tone signal source and said tonecolor filter;

a source of reiteration voltage;

means rendering one of said gates reiteratively uninhibited in response to said reiteration voltage;

a' source of key controlled randomly occurring control pulses; and

means for uninhibiting the other of said gates in response to said control pulses.

18. The combination according to claim 17, wherein is included:

an array of solo keys;

an array of accompaniment keys;

means responsive to actuation of said accompaniment keys for connecting said tone signal sources in cascade with said gate according to the keys actuated; and

means responsive to actuation of any one or more of said solo keys for generating said control pulses. 19. In a music system: a keyboard instrument having arrays of keys calling forth notes of the musical scale, when said keys are actuated; means responsive to actuation of certain of said keys for providing control voltage during actuation thereof;

means for calling forth electrical tone signal from said instrumcnt in response to actuation only of others of said keys; and

means for converting said electrical tone signals to acoustic signals only in response to said control voltage.

20. The combination according to claim 19, wherein is further provided means for reiterating said acoustic signals.

21. An electronic musical instrument having a gamut of solo keys and a gamut of accompaniment keys:

means responsive to actuation of selected ones of said accompaniment keys for sounding corresponding accompaniment tones; and

means responsive to continuous and uninterrupted'actuation of selected ones of said accompaniment keys only with concurrent actuation of selected ones of said solo keys for sounding said accompaniment tones in response to each actuation of any one of said solo tones during said uninterrupted actuation of said selected ones of said accompaniment keys.

Claims

1. In an electronic organ having a gamut of tone signal sources, a first keyboard, a second keyboard, a first tone-color filter, a second tone-color filter, an output system, a first key switch operable by a key in said first keyboard and coupled between one of said sources and said output system via said first tone-color filter, a second key switch operable by a key in said second keyboard and coupled between another of said sources and said output system via said second tone-color filter the combination comprising: a direct current supply; an auxiliary key switch ganged to said first key switch; a trigger and pulse-shaping circuit means coupled between said auxiliary key switch and said direct current supply and responsive to closure of said auxiliary key switch for generating a control pulse; and a normally-inhibited gate coupled to said trigger and pulseshaping circuit, and responsive to said control pulse to uninhibit said gatE, said gate being also coupled between said second key switch and to said first tone-color filter, whereby actuation of said key in said first keyboard closes said auxiliary key switch creates a pulse in said trigger and pulseshaping circuit operative to uninhibit said gate so as to cause a signal to flow between said other source and said output system via said second key switch and said first tone-color filter when said key in said second keyboard is actuated.

2. The combination according to claim 1, including: a third tone-color filter; a third key switch operable by said key in said first keyboard and coupled between a further one of said sources and said output system via said third tone-color filter; a fourth tone-color filter; a fourth key switch operable by said key in said second keyboard and coupled between one of said sources and said output system via said fourth tone-color filter; and a second normally-inhibited gate coupled to said trigger and pulse-shaping circuit, and responsive to said control pulse to uninhibit said gate, said second gate being coupled between said fourth key switch and said third tone-color filter, whereby actuation of said key in said first keyboard closes said auxiliary key switch, thereby creating a pulse in said trigger and pulse-shaping circuit operative to uninhibit said second gate and to cause a signal to flow between said one of said sources and said output system via said fourth key switch and said third tone-color filter, when said key in said second keyboard is actuated.

3. The combination according to claim 1, including a reiteration gate coupled between said second key switch and said second normally-inhibited gate; a reiteration oscillator coupled to said reiteration gate for rendering said reiteration gate reiteratively inhibited and uninhibited; and switch means coupled between said reiteration gate and said reiteration oscillator.

5. The method of automatically coupling a signal derived from closing a key switch in one keyboard to a tone-color filter for another keyboard which comprises: deriving a pulse from depression of any key in said other keyboard; amplifying and shaping said pulse; and applying said pulse to uninhibit a normally inhibited gate operative between said key switch in said one keyboard and said tone-color filter.

6. In an electronic organ; a series of tone signal sources; an array of solo keys; an array of accompaniment keys; a solo tone color filter; an accompaniment tone-color filter; a loudspeaker system connected in cascade with said tone-color filters; means responsive to actuation of selected ones of said solo keys for connecting corresponding ones of said tone signal sources to said solo tone-color filters; means responsive to actuation of selected ones of said accompaniment keys for connecting corresponding ones of said tone signal sources to said accompaniment tone-color filter; and gate means responsive to actuation of any one or more of said solo keys for connecting tone signal sources called for only by the actuated accompaniment keys to said solo tone-color filter.

7. The combination according to claim 6, wherein said gate means is arranged and adapted to be operative while said any of said solo keys are actuated for the duration of the actuation.

8. The combination according to claim 6, wherein said gate means is arranged and adapted to be only transiently operative in response only to initial actuation of any said solo keys regardless of the then actuated condition of other of said solo keys.

9. In an electronic organ: a series of tone signal sources; a array of solo keys; an array of accompaniment keys; a solo tone-color filter; an accompaniment tone-color filter; a loudspeaker system conNected in cascade with said tone-color filters; means responsive to actuation of selected ones of said solo keys for connecting corresponding ones of said tone signal sources to said solo tone-color filter; means responsive to actuation of selected ones of said accompaniment keys for connecting corresponding ones of said tone signal sources to said accompaniment tone-color filters; means responsive to actuation of any one or more of said solo keys for connecting tone signal sources corresponding only with the actuated accompaniment keys to said solo tone-color filter, wherein is provided a selective two-condition switch; and means comprising a pulse shaping circuit responsive according to the condition of said selective two-condition switch for connecting tone signal corresponding with accompaniment keys to said solo tone-color filter transiently on actuation of any of said solo keys or for the duration of actuation of said solo keys.

10. The combination according to claim 9, wherein said last means includes a normally nonconductive transistor and a normally conductive transistor connected in cascade: means responsive to rendering said normally nonconductive transistor conductive to render said normally conductive transistor nonconductive; a gate connected between said tone sources and said solo tone-color filter; means uninhibiting said gate in response to the conductive condition of said normally conductive transistor and inhibiting said gate in response to the nonconductive condition of said normally conductive transistor; and means applying to said pulse to render conductive said normally nonconductive transistor selectively on a transient and a steady state basis.

11. In an electronic organ: a source of negative voltage; a resistance connected in series with said source of voltage; a plurality of load circuits selectively connected in cascade with said resistance; a plurality of key switches; means responsive to closure of any one or more of said key switches for completing a circuit from said source of voltage through said resistance to one or more of said load circuits to develop a control pulse; a first transistor having a base, an emitter and a collector; means connected said base to the load side of said resistance and said emitter directly to said source of voltage; an emitter resistance connected between said emitter and a reference point; a collector resistance connected between said collector and said reference point; a gate inhibited by negative voltage applied to a gating electrode; and means controlling said gate at said gating electrode selectively directly from said emitter or in response to voltage developed across at least part of said collector resistance.

12. The combination according to claim 11, wherein said gate includes: a capacitor connected between said gating electrode and a reference point; a terminal; means for at will selectively connecting said capacitor to said emitter and to said terminal; and means for discharging said capacitor in response to said control pulse developed across said resistance when said capacitor is connected to said terminal.

13. A gating circuit comprising: a NPN transistor having a base, an emitter and a collector; a source of negative voltage connected to said emitter; a load resistance connected between said collector and ground; a load capacitor having a first electrode connected to ground and having a second electrode; a timing resistance connected in series between said second electrode and said collector; a diode connected across said timing resistance poled in discharge relation to said capacitor through said transistor; means connected to said base for maintaining said transistor normally conductive; mean means for randomly rendering said transistor nonconductive; a gate having a control terminal, a signal input terminal and a signaL output terminal; means connecting said control terminal to said second electrode; a source of tone signal connected to said input terminal; and a load connected to an output circuit, said gate being of the type inhibited by negative voltage.

14. In an electronic organ: a tone generator including a gamut of tone signal sources; a first tone-color filter; a second tone-color filter; a loudspeaker system connected to said tone-color filters; a first array of keys for calling forth tones in response to said tone signal sources via said first tone-color filters; and means responsive to actuation of any of a said first array of keys for calling forth tones from said tone signal sources at pitches selected by keys of said second array of keys.

15. The combination according to claim 14, wherein said last means includes; means for generating a control pulse in response to each actuation of any one or more of said first array of keys; a collector for all tone signals called for by actuation of said second array of keys; a normally inhibited gate connecting said collector with said first tone-color filter; and means responsive to said control pulse for uninhibiting said gate.

17. In an electronic organ; a source of an array of tone signals arranged according to the equally tempered scale; a tone-color filter; a first normally inhibited gate; a second normally inhibited gate; means connecting said gates in cascade with each other between said source of tone signal source and said tone-color filter; a source of reiteration voltage; means rendering one of said gates reiteratively uninhibited in response to said reiteration voltage; a source of key controlled randomly occurring control pulses; and means for uninhibiting the other of said gates in response to said control pulses.

18. The combination according to claim 17, wherein is included: an array of solo keys; an array of accompaniment keys; means responsive to actuation of said accompaniment keys for connecting said tone signal sources in cascade with said gate according to the keys actuated; and means responsive to actuation of any one or more of said solo keys for generating said control pulses.

19. In a music system: a keyboard instrument having arrays of keys calling forth notes of the musical scale, when said keys are actuated; means responsive to actuation of certain of said keys for providing control voltage during actuation thereof; means for calling forth electrical tone signal from said instrument in response to actuation only of others of said keys; and means for converting said electrical tone signals to acoustic signals only in response to said control voltage.

21. An electronic musical instrument having a gamut of solo keys and a gamut of accompaniment keys: means responsive to actuation of selected ones of said accompaniment keys for sounding corresponding accompaniment tones; and means responsive to continuous and uninterrupted actuation of selected ones of said accompaniment keys only with concurrent actuation of selected ones of said solo keys for sounding said accompaniment tones in response to each actuation of any one of said solo tones during said uninterrupted actuation of said selected ones of said accompaniment keys.