Phase Distortion

Keep the waveform and bend its phase; a sine gains the edge of a sawtooth.

Related

TimbreSynthesizerThe software synthesizerModern

The question

A filter darkens by removing highs, yet phase distortion brightens a sine without removing anything. What changes, and why does it read as a sawtooth without orderly harmonics?

How it works

Phase distortion speeds up or slows the read-through of one cycle, drawing a bend into the phase. The wave is still a sine, but phase no longer advances evenly, so energy is redistributed and saw-like edges appear. Casio's CZ range did this with digital lookup tables, modulating the read phase rather than the frequency. A wavetable swaps the whole wave; phase distortion changes only the reading path. Without a filter, high partials survive far up.

Settings and what you hear

At low amounts the tone merely hardens. Push further and a clear resonant peak and metallic colour appear. Placing the phase break at different points produces vowel-like or woody resonances. An envelope on the distortion amount can make the attack hard and the tail soft. Very steep bends add harsh highs, and the level can jump.

What to listen for

Hear a pure sine, then the distorted version; brightness rises while the fundamental stays fixed. Compare it with a sawtooth; its upper partials are less regular and carry a metallic taste. Last, hear the attack: as the amount falls with the envelope, the sound rounds off.

Common misconceptions

That phase distortion is a phaser; that it needs a filter; that digital synthesis must be cold, when it can be round and vocal.

Sources

• Casio CZ-101 Owner's Manual — phase distortion description checked, not quoted
• Curtis Roads, The Computer Music Tutorial — digital synthesis methods checked, not quoted

Used for fact-checking only; all prose is original.