Electronic musical instrument circuit

TLDR: A key actuated electronic musical instrument of the type suitable for use with piano or organ keyboards, or the like, has a single relaxation oscillator circuit for producing melody tones from selected keys of a keyboard.

Abstract: A key actuated electronic musical instrument of the type suitable for use with piano or organ keyboards, or the like, has a single relaxation oscillator circuit for producing melody tones from selected keys of a keyboard, and three relaxation oscillator circuits for producing chord tones from other selected keys of the keyboard. A delta pitch circuit which produces a sawtoothlike output signal is coupled to one of the inputs of the single oscillator to provide a rapidly changing sound going from a flat tone to a natural tone. The signals for producing melody sounds are delivered through a selective filter circuit which will selectively simulate the sounds of, for example, a saxophone, brass, horn, or a string instrument. The sound signal from the filter circuit is then delivered to an audio amplifier and loudspeaker system. The three oscillator signals for producing chord sounds are mixed together in a transistor buffer stage and then delivered to the audio amplifier through a gate circuit formed by a light-emitting diode and a light-dependent resistor. The gate circuit is responsive to an automatic rhythm generator so that chord sounds may have a selected rhythm. Also connected to the audio amplifier is the automatic rhythm sound generator which can play one of several rhythms utilizing desired percussion sounds. An adjustable vibrato circuit is connected to the melody oscillator to produce a pulsating sound that can be varied in frequency.