JPS54148520A - Electronic musical instrument - Google Patents

Abstract

PURPOSE: To form musical tone waveform signals of intricate timbres with a simple constitution by performing operations based on the specified modulation system with basic waveforms as triangular waves.

CONSTITUTION: According to key touching, frequency width codes are read out from a frequency memory 12 via keyboard circuit 11 and the signals corresponding to the phase angle θ of the modulating signal and the phase angle θ of the muscial tone are inputted to accumulators 13, 14. At the samt time, a modulating index generating circuit 15 generates the signal corresponding to a modulation index A which changes timbres, according to the key-ON signal. Inputting of these signals from the accumulators 13, 14 and circuit 15 causes the basic wave musical tone forming signal T(θ) corresponding to the pitch from the triangular wave generating circuit 2 of a musical tone forming circuit 1 to be modulated through operations based on formula I in a multiplier 3, a bit number increasing circuit 4, an adder applied with the index 4, etc. and in turn the musical tone waveform signals of intricately changing timbres are generated from a triangular wave generating circuit 6 with the simple constitution of not using plural sets of sine tables, etc.

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