Binary interpolator for electronic musical instrument

Abstract

A binary interpolator circuit is embodied in an electronic musical instrument for producing a relatively smooth, inaudible transition between steps of different amplitude in a stepwise advancing or decreasing waveform, such as an envelope signal for a note from a percussive type instrument or voice such as a piano. The binary interpolator circuit includes a counter circuit for producing a sequence of stepwise changing binary coded signals and a combining circuit for combining the interpolating signals, in the sequence produced, with a binary coded scaling signal corresponding to the amplitude difference between the two points in the stepwise changing waveform between which interpolation is desired. A comparator circuit compares the interpolating signals, in the sequence produced, with the scaling signal and produces an output control signal for indicating whether the binary coded numbers corresponding to the respective interpolating and scaling signal are equal. A control circuit is responsive to this control output signal for respectively allowing or inhibiting the production of the interpolating signals. In a preferred embodiment, multiplexing and demultiplexing circuits are provided for serially multiplexing a plurality of waveforms to be interpolated and simultaneously serially multiplexing a plurality of interpolating signals for combining at the combining circuit. Demultiplexing circuits are provided for serially outputting both the control signals and the waveforms thus interpolated.