A stereo chorus: a short delay whose time drifts slowly, blended with the original sound. It detunes and blurs a voice so a thin patch or a clean guitar sounds wider, without adding a single note.
The idea
As the delay time moves, the delayed copy bends slightly sharp and then slightly flat. Heard together with the dry signal, the two copies interfere, and that shifting interference is the chorus sound. Chorus runs one delay line per side, with the left and right sweeps moving in opposite directions, which is what spreads the sound across the stereo field.
