JPS54161314A - Electronic instrument - Google Patents

Abstract

PURPOSE: To simplify an electronic instrument by synchronously scanning the desired portion including the condenser of each key of an envelope forming portion so that an envelope generating circuit is controlled by time sharing multiplex key signals resulting from depressions of plural keys.

CONSTITUTION: A switch, which corresponds to each key of a key board 7, and the pairs of condensers 101 and 201, 102 and 202, and so on, which are composed of such condensors as correspond to the respective keys of an envelope forming portion 12 so that their charging and discharging operations are reversed upon the depressing and releasing operations of the keys through the inverter 32 and FET of an envelope waveform generating circuit 33, are synchronously scanned with the same clock. On the other hand, the transistor 15 and inverter 32 of the circuit 33 are supplied with the series time sharing multiplex key depressing signals coming from a time sharing multiplex converting portion 8 which is composed of a multiplexer or the like when a plurality of the keys are depressed. As a result, the circuit 33 generates the envelope waveform signals corresponding to the plural key depressions in a time sharing manner to control such a grade waveform in an envelope manner as is scanned with the same clock to close and open a gate while corresponding to the key depressions so that the musical sounds can be generated through a mixing portion by a simple construction using the single envelope genenerating circuit.

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