Quasi-random phase shift system for an electronic musical instrument

Abstract

An electronic musical instrument employing top octave synthesizer circuits (TOS circuits) for generating the musical tones to be reproduced by the instrument employs a single master oscillator common to all of the top octave synthesizer circuits for supplying the trains of clock pulses to the synthesizer circuits for their operation. To prevent phase-locked conditions from existing in the frequencies produced by different synthesizers, the clock pulses from the master oscillator are supplied to the synthesizers through coincidence gate logic circuitry which is controlled by means of a low frequency oscillator and a divider or shift register circuit to delete different ones of the clock pulses from the clock pulse signal trains for each of the different synthesizers. This causes all of the frequencies obtained from the synthesizers to be slightly different from one another, independent, and not phase-locked. This nonphase-locked system provides a more pleasing musical effect than is otherwise attainable from a top octave synthesizer system using a single master oscillator to drive more than one top octave synthesizer circuit.