A delay records the incoming signal and plays it back a moment later. Feeding part of the output back into the input produces a series of repeats, and the delay time can be set in milliseconds or locked to the tempo of the track. Before digital units, echo was made with tape: Roland’s RE-201 Space Echo of 1974 ran a tape loop past three playback heads, with tape speed setting the delay time, and its imperfect transport gave the repeats a soft, wavering quality.
In jazz lo-fi, delay is usually discreet: a few warm repeats on a guitar phrase, a muted trumpet or a vocal chop, often filtered so that each echo grows darker. In audio engineering the word also means simply a time lag, called latency in computer audio.