Patent GB-1370128-A (GB)
Title: Automatic chord and rhythm electronic organs
IPC: G10H1/40
Filed: 1971-09-07
Abstract: 1370128 Electrical musical instruments D H BALDWIN CO 7 Sept 1971 [9 Sept 1970] 41730/71 Heading G5J A device provides a conventional electronic organ with automatic chord selection and/or an automatic rhythm accompaniment. Playing of only one note distributes root, third and fifth parts of the chord between pedal and manual sections of the organ in any one of five rhythms, rhythm percussive effects also being provided if desired. A touch bar is provided to convert from major to minor chords. The pedal and/or manual notes may be played continuously while the percussion section is rhythmically pulsed. Playing of two notes removes the chord accompaniment and of three notes results in conventional operation of the organ. The rhythms are provided by a ramp generator (1) (Fig. 1, not shown) which is switched off or on by a transistor (40). For waltz rhythm, during each measure, (Fig. 2, not shown), two chords are played and the circuitry ensures that a downbeat, e.g. the chord root, is always played initially when the key is pressed, for all rhythms. At successive measures of the waltz downbeats are provided by the fifth part of the chord when a capacitor (2) discharges. Transistor switches (54), (56) fire at voltages U 2 , U 1  (Fig. 2, not shown) to provide pulsing of the chords. For rock, or other rhythms, the terminals (72), (74), (Fig. 1), are shorted, resulting in earlier discharge of capacitor (2) at a voltage half that for the waltz. Additionally, the transistor switches now fire at ¢ and 3/4 of V 3 , the voltage at which the capacitor discharges (Figs. 2, 3, not shown). Transistor 40 is under control of the keyboard so that depression of a key activates the ramp generator. The key circuitry, Fig. 4, has key contacts 100, the corresponding root note being indicated against each contact. Depression of a key closes a corresponding contact 100 and connects a voltage bus 102 to a corresponding diode gate. The diode gate connects the chord major and minor third parts, provided by two of the sources D# to D 1  to buses 116, 132. Which one of buses 116, 132 carries the major part is determined by the chord selected. In addition, root and fifth parts of the chord, provided by sources C to F, appear on buses 154, 156, which one of said buses carrying the root again being dependent upon the selected chord. A voltage appears on one of control signal buses 161 or 144 to provide an indication as to which buses carry the root and major parts. The buses are connected to further circuitry, Fig. 6. A touch bar 164 is provided which in its normal position allows the major chord of the selected note to be played. If the touch bar is in the normal position and a selected note results in activation of bus 144, transistor 160, via transistors 170, 172 cuts off transistor 174, carrying the minor third part of the chord and switches on transistor 176, carrying the major third part. Therefore the major chord can be played through, the minor part being blocked. Depression of the touch bar switches off transistor 176 and turns on transistor 174, resulting in transmission of the minor chord. When a voltage appears on bus 161, the circuitry compensates for the reversal in roles of buses 116, 132 and major, minor chords are again played in the normal and depressed condition of the touch bar respectively. Transistors 160, 184 also control a flip-flop which is associated with the root and fifth parts of the  chord, the flip-flop controlling transistors 206, 208, connected to buses 154, 156, carrying the root and fifth parts. The flip-flop determines which one of transistors 206 or 208, is conductive and therefore whether the root or fifth part is played through, the circuit being arranged so that the appropriate transistor always transmits the root on the initial downbeat (Figs. 2, 3, not shown). The flip-flop is also controlled by the rhythm section which determines whether a root or fifth should be played through on a particular beat of the rhythm selected. Transistors 206, 208 transmit through diode gates 209, 211. The various parts of the chord are mixed in amplifier 214 and then passed to the manual filters (218) (Fig. 5, not shown). Diode gates 209, 211 and further gates 179, 187 carrying the major and minor parts are pulsed by the rhythm section. The root or fifth is also passed to transistor 215 and then to a pedal divider (216) (Fig. 5), the pedal circuit also being pulsed at gate (240) by the rhythm section. A switch 220 (Fig. 6) is also provided which enables the root to be sounded continuously through the pedal circuit, gate- (240) being maintained open by voltage from terminal 219. The rhythm section comprises a rhythm selection switch (Fig. 7), the contants of which activate the circuitry according to the selected rhythm. Assuming a rhythm has been selected and if a key is depressed, the initial downbeat pulse provided by the ramp generator fires a transistor (282) (Fig. 8, not shown), the transistor actuating gates in the organ via terminal (288) to sound a selected bass rhythm accompaniment, e.g. bass, drums, cymbals &c. if required. Transistor (282) also pulses a terminal (310) (Fig. 5, not shown) connected to the pedal diode gate (240). The gate passes the root part on first and corresponding alternate downbeats through the pedal circuit and the fifth part on second and corresponding alternate downbeats (see waltz, rock rhythms, Figs. 2, 3), the root fifth selection being performed by the flip-flop. Therefore, the bass percussion voices are sounded with the root and fifth in alternation on each downbeat. If a waltz has been selected, on the second beat, transistor (266) (Fig. 8, not shown) is triggered which, via a transistor (292) triggers an accompaniment rhythm percussion section to sound snare drum, brush, block &c. In addition, transistor (266) is coupled to a sustain capacitor (296) connected to gates 179, 187, 209 and 211, of Fig. 6. When the transistor is pulsed, capacitor 296 becomes fully charged, opening the gates, the selected chord being played through the lower manual at full volume. A potentiometer 300, Fig. 6, connected to the capacitor determines the rate of decay of the capacitor voltage and the amplitude to which it decays. Therefore a chord of initial maximum amplitude is played which decays at a rate and to an amplitude selected by the player. Appropriate setting of the potentiometer allows the lower manual notes to be played continuously. On the third beat, transistor (266) is again pulsed due to the rhythm select switch setting, in accordance with the waltz rhythm (see Fig. 2). Finally, the sawtooth is terminated, corresponding to a downbeat, transistor (282) being pulsed and the flipflop being reset to pass the fifth part to the pedal circuits, the sequence then being repeated continually until the key is released. Selection of other rhythms results in modified action of the circuits, e.g. the flip-flop and switches (54), (56), to produce the desired downbeats, chords, bass accompaniment &c. A tempo light (274) (Fig. 8, not shown) operates at the beginning of every measure of the selected rhythm i.e. at the start of every ramp for waltz and every other ramp for other rhythms (Figs. 2, 3, not shown). Transistors 374, 376, 378, 380 (Fig. 7) constitute the major part of the circuitry for determining whether one, two or three notes have been selected. Transistor 374 is conductive when a single key is pressed and, via bus 382, controls transistor (40) (Fig. 1, not shown) to operate the ramp, i.e. rhythm, generator. When two keys are pressed sufficient current is supplied (from bus 102 of Fig. 4) to turn on transistor 378 and in turn switches off transistor 374, which controls transistor (40), to disable the rhythm generator. The same action occurs when three keys are pressed, but additionally, transistor 380 is made conductive, which via lead 412 and transistor (414) (Fig. 8, not shown) turns on FET 420. The FET therefore connects terminal U, to which all the lower manual notes are applied, to terminal A (see also Fig. 5, not shown) so that the lower manual is connected directly to the speaker system enabling normal organ operation. Various other secondary parts of the circuitry ensure proper operation of the organ in the event of erroneous use of the device by the player. Closure of the rhythm only switch, Fig. 7, turns on FET 420, allowing normal organ operation as above, disables the single note chord operation, and results in rhythm percussion accompaniment independent of the keyboard at the selected rhythm.