Simultaneous voice pitches in a polyphonic tone synthesizer

摘要

In a musical instrument having one or more tone generators in which a plurality of data words corresponding to the amplitudes of a corresponding number of evenly spaced reference points defining the waveform of an audio signal are transferred sequentially from a note register to a digital-to-analog converter in repetitive cycles at a rate proportional to the pitch of the tone being generated, apparatus is provided for simultaneously creating tones at two different pitches. The reference points are computed using specified wave shape symmetry characteristics such that a single variable frequency oscillator suffices to generate both tone pitches without requiring separate, or time shared, tone generation channels.