AN-11: Phase Distortion Synthesis
by Davis Sprague
This App Note demonstrates basic phase distortion synthesis theory, and the companion plugin allows a variety of phase distortion controls producing many interesting waveforms. Davis Sprague wrote this App note as a senior Music Engineering student in the University of Miami’s Music Engineering Technology program – he is now a Software Engineer at Korg Research and Development. PD synthesis can produce aliased waveforms, and alias suppression is accomplished with BLEP. However, as Mr. Sprague points out, there are some waveforms for which this kind of correction is useless so you will need to address aliasing with other methods such as oversampling. The code is well commented and easy to read. The sawtooth waveform below is created by distorting the phase increment pointer in a sinusoidal wavetable. Davis also demonstrates using the PD method to create waveforms that appear to be filtered with a resonant lowpass filter, when in fact PD synthesis is filter-less.