Pulse-width modulation

Pulse-width modulation (PWM) varies a pulse wave's duty cycle — the fraction of each cycle spent at its high level — changing timbre while pitch holds still.

A pulse's harmonic recipe depends entirely on its width, sweeping from hollow at 50% through nasal toward thin, reed-like slivers near the extremes; animating that width is a staple of classic synth motion. Wavetables encode the effect as a run of frames at decreasing widths, so wavetable position becomes the width control — and because adjacent widths are so alike, it is one of the smoothest sweeps a table can make.