Abstract: An electronic organ uses several top octave synthesizer circuits for producing the various tones used in the organ. Each of the top octave synthesizers is capable of producing any tone which can be produced by the organ. As a consequence, the outputs of each synthesizer are applied to a coupler circuit, which in turn is connected to an octave assignment switching tree for directing the tones coupled to the inputs of the switching tree to individual leads, each corresponding to a different octave in the range of tones produced by the organ. The similar octave leads from each of the different octave switching circuits are connected together to common flute octave buses, so that the filters connected to the output buses have substantially fewer tones appearing at the input than one which would have the full tone range of the organ. Typically, the range of tones appearing at a filter input is one octave or less.

Abstract: A limited number of top octave synthesizer tone generating circuits for producing various tones are used in an electronic organ. Each of the top octave synthesizer circuits is capable of producing any tone which can be produced by the organ. An assignment circuit is employed to assign different ones of the top octave synthesizers to produce the tones represented by different key closures. Because of the limited number of tone generator circuits employed, it is possible under some circumstances to attempt to cause the organ system to produce root tone outputs in excess of the number of top octave synthesizer circuits used in the system. When this occurs, a root tone for a new note is assigned to the top octave synthesizer circuit which is farthest into its decay mode of operation, thereby terminating the tone previously produced by that top octave synthesizer circuit earlier than would be the case if the full decay of that tone were permitted to take place.

Abstract: A digital keying system for an electronic musical instrument, such as an electronic organ, comprises a digital percussion generator which synchronizes the operation of a variable attentuator with the zero crossings of a sine wave signal applied to the input of the attenuator from a waveform generator. Pulses from a rhythm generator are applied to a coincidence gating circuit along with pulses corresponding the zero crossings of the sine wave signal from the waveform generator to synchronize the stepped operation of the variable attenuator with the zero crossings of the sine wave signal applied to it.

Abstract: A digital keying system for an electronic organ comprises a voltage divider network consisting of weighted value resistors switched into or out of the circuit by corresponding switches. The network is connected to a tone signal output terminal, and a reversible counter is connected to control the states of conduction of the switches. Closure of a key-operated switch causes clock pulses from an attack clock pulse source to be applied to the reversible counter to selectively control the operation of the switches to shape the attack waveform of tone signals appearing on the output terminal as determined by the pattern of operation of the switches. Upon release of the key, clock pulses from a decay clock generator are applied to the counter to operate it in the reverse direction, establishing a decay envelope for the tone signal in accordance with the pattern of operation of the switches.

Abstract: An electronic musical instrument, such as an organ, includes a multiplexing system for simultaneously scanning key switches on all of the manual keyboards and pedalboards sequentially an octave at a time and further for simultaneously and sequentially scanning all coupler controls to produce a digital output signal having pre-assigned positions for each of the different notes represented by operation of a coupler switch or a key switch in all of the coupler control sections and the keyboard sections of the organ. This digital signal is supplied to de-multiplexer keyer circuits for reproducing sound signals supplied to the output loudspeakers of the organ.

Abstract: A keyboard electronic musical instrument includes a plurality of playing keys, each of which are capable of coupling a set of chord tone signals to an output utilization circuit. These chord tone signals comprise the root and fifth parts and also the major third and minor third parts of a chord. Each of the playing keys are capable of operation to two different depressed positions, one of which causes the major third chord component to be supplied along with the root and fifth parts to the utilization device. The other depressed position of the key causes the minor third chord component to be supplied along with the root and fifth parts to the utilization device. Provision also is made for permitting only the root note tone signal to be passed to the output circuit to permit normal playing of the keyboard.

Abstract: A rhythm system includes a memory for storing rhythm patterns, with a plurality of sections for controlling individual rhythm instruments, and instrument generators for producing sounds in accordance with the patterns. The patterns are stored in memory lines, with the number of counts in the patterns differing from one pattern to another. A plurality of short rhythm patterns can be stored on a single memory line. The system includes pushbutton switches for selecting the particular rhythm patterns and automatically selects the proper clock frequency for timing the selected rhythm pattern. The system is automatically reset at the end of the pattern and can selectively reset at the beginning of an intermediate position in the memory line, as required when a plurality of rhythms are stored in sequence on a single line. The system can also provide a special rhythm, such as a drum break, and this can be inserted during the playing of a selected continuous rhythm.