Pulse-width modulation

Pulse-width modulation (PWM) varies a pulse wave's duty cycle. The duty cycle is the fraction of each cycle spent at its high level, and changing it changes the timbre.

A pulse wave's harmonic amplitudes depend on its width. At 50%, it contains odd harmonics; other widths change that balance. A wavetable can store successive pulse widths as frames, allowing position to control the stored width sweep. Similar widths in adjacent frames usually produce a smooth transition.