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Abstract

An electronic piano includes a tone generator having a pulse generator and a discrete TOS circuit for each octave. The input of the first TOS circuit is connected with the pulse generator and the input of each next-following TOS circuit is connected with the input of the preceding TOS circuit by a divide-by-two divider circuit. The outputs of each TOS circuit are connected with discrete control circuits each having an analog switch for each output of the respective TOS circuit. First inputs of the analog switches receive envelope control voltage signals on depression of the respective piano keys while second inputs of the analog switches receive tone signals from the corresponding outputs of the respective TOS circuits. The outputs of the analog switches transmit tone signals, which are modulated as a function of the intensity the corresponding envelope control voltage signals, to a loudspeaker by way of either one of two main branches of the respective control circuits. The intensity of the envelope control voltage signals depends on the lengths of the intervals during which the corresponding keys move from undepressed to depressed positions. Key contact transients are eliminated from the modulated tone signals by superimposing thereon inverted d-c voltage signals whose amplitude is half the amplitude of the modulated tone signals. The dynamic volume range of the modulated tone signals is close to the range of tone volumes in a mechanical piano.

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