Importance

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Abstract

An audio synthesis circuit is disclosed that can generate multiple audio tones, or operators, each having different harmonic characteristics. The audio synthesis circuit can be used in a time-multiplexed fashion so that the multiple audio tones, or operators, can be computed in a single audio synthesis cycle and then combined to form voices/channels. Each audio synthesis cycle can be divided into as few as 0 or as many as 48 time slots, meaning that as many as 48 operators can be played simultaneously. The disclosed circuit provides a preset organization of the 48 operators into 12 2-operator channels and 6 4-operator channels. These channels can be played in various system modes, including backward-compatible 2- and 4-operator modes in which the programming of the operators is restricted, and an enhanced mode, in which the operators can be freely programmed. In the backward-compatible modes, two operators of each 4-operator channel are constrained to be duplicates of a respective 2-operator channel. Consequently, it is not possible for two different 2-operator voices to be made by playing one four operator voice in the 2-operator mode. Instead, when a 4-operator voice is played in the 2-operator mode, only one two-operator channel results, using the non-duplicated operators. Similarly, playing a 4-operator channel in 4-operator mode turns off the corresponding 2-operator channel, and playing a 2-operator voice turns off the duplicate operators of a later-activated 4-operator voice.

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First Claim