Abstract: For generating tones in an electronic musical instrument, there are provided multiple master frequency sources, a different source for each octave, differing in frequency from each other by a factor which differs from two by at least one semitone, each of which is coupled to a respective frequency synthesizer all of which have the same dividing ratios, to divide down the frequency of its master frequency source to pitches of the twelve notes in the intended octave. In one embodiment the sources are separate master clock pulse sources, and in another embodiment a pulse train derived from a single clock pulse source is applied to the frequency synthesizer for the highest octave, and the pulse train applied to each of the other synthesizers is derived from the pulse train supplied to the frequency synthesizer for the next highest octave by dividing the pulse repetition frequency thereof by a factor which differs from two by one or more semitones.

Abstract: For reiteration of percussive sounds in an electronic organ there is provided a circuit for generating pulse signals for reiteration control which are "on" for much longer periods than they are "off", thereby substantially reducing the chance of an organ key being actuated when the control signal is in its "off" condition. The circuit is so arranged that playing of an additional key at a time when one or more other keys are being held has no effect on the reiteration of the sound produced by the held keys. The circuit generates four control signals which are connected such that each controls three notes in a given octave on the keyboard, a different three in successive octaves, such that when normal intervals (e.g., thirds, fourths and fifths) are played, the effect of random reiteration control is produced.

Abstract: In an electronic musical instrument, such as an electronic organ, the speech characteristics of Vox Humana and similar reed organ pipes are simulated by applying a repeating series of pulse groups separated from each other, which groups each contain a short sequence of two or more pulses, to a sharp cutoff low-pass filter for converting the series of pulse groups into a sound producing signal simulative of the sound signal produced by a Vox Humana or similar organ pipe. The repeating series of pulse groups is obtained by nonlinearly combining square wave tone signals from two or more different octaves of a conventional phase-locked tone generator. The synthesized repeating series of pulse groups, one series for each note of the instrument, are applied to a single low-pass filter, or grouped and applied to a small number of filters.