Add echo and delay, from slapback to dub

How echo and delay work

Three controls, and what each does

A delay stores the signal, waits, and plays it back alongside the original. Delay time sets how long it waits — that is the gap you hear between the word and its repeat. Feedback sends the output back into the input, so each repeat spawns another and the echo trails off over several repetitions instead of happening once. Wet mix sets how loud the repeats are against the dry signal.

Feedback near maximum never decays, and the sound builds until it overloads. It is an effect, but use it knowingly.

Timing the delay to the song

A delay set to a random time fights the music; one set to the beat disappears into it. The arithmetic is simple: milliseconds per beat equal 60000 divided by the tempo in BPM. At 120 BPM a beat is 500ms, so 500 gives quarter notes, 250 gives eighths and 375 gives a dotted eighth — the setting behind a great many guitar parts.

Short delay, long delay

Under about 50ms the repeat is too close to be heard separately and thickens the sound instead — the doubling effect on countless vocals. Around 80-120ms you get slapback, the single tight repeat of early rock and roll. Beyond roughly 300ms each repeat is a distinct echo, which suits sparse arrangements and gets muddy in busy ones.

Delay is not reverb

They are often confused. A delay produces countable repeats. Reverb produces thousands of reflections too dense to separate, heard as a space rather than as echoes. Delay places a sound in time; reverb places it in a room. Many mixes use a little of both.