Chorus

A chorus copies the incoming sound, delays the copy by a short time (under about 30 milliseconds, too short to hear as an echo), and uses a slow LFO to keep lengthening and shortening that delay. While the delay grows, the copy sounds a touch flat; while it shrinks, a touch sharp. Mixed with the original, that gives a moving detune on everything the instrument plays. A stereo chorus wobbles the left and right copies out of step with each other, which is where the width comes from.

Typical controls, with starting points:

• Rate: 0.3 to 1 Hz. Slower sounds lush, faster starts to sound like vibrato.
• Depth: low to middle. Deep and fast together sounds seasick.
• Mix: 30 to 50%. Fully wet leaves no steady original, so you hear vibrato instead of chorus.

Chorus is a classic partner for electric piano, clean guitar, strings and pads. The Boss CE-1 Chorus Ensemble pedal from 1976 used the chorus circuit from Roland’s Jazz Chorus amplifier, and the chorus built into Roland’s Juno-60 and Juno-106 is a big part of their pad sound. Some gear uses the name ensemble for a richer chorus with several wobbling copies.

Synths and keyboards often have it as a Chorus switch or knob, and most DAWs include a chorus plugin. Keep it off the deepest bass notes, since the stereo copies can cancel on a mono speaker, and use it sparingly on acoustic piano, where the wavering pitch reads as out of tune.

Gelato Synth has a Chorus slider on its Osc B page, and Gelato Chord includes chorus in its FX alongside reverb and delay. How to make a synth sound bigger shows how chorus stacks with detune, and the LFO guide explains the slow oscillator doing the wobbling.