Electronic musical instrument using FM sound generation with delayed modulation effect

摘要

A computer having one or more wave tables stored therein is used to synthesize sounds represented by a series of digital samples produced at a sample rate by specifying parameters including a carrier frequency, a modulating frequency and an index of modulation. At each sample time, a modulation value determined during an immediately preceding sample time is scaled to produce a digital control signal. Also at each sample time the modulation value to be used during an immediately succeeding sample time is read from a location of a wave table determined by the modulating frequency, and a carrier value used to produce the digital samples is read from a location of a wave table determined by the carrier frequency and the digital control signal. Modulation effects are therefore delayed by one sample in order to speed execution of the method using the computer. Phase accumulation is performed using a multiplier making it unnecessary to store the sum of all of the previous steps as would be otherwise be required using an additive approach.