Slap Back

The term slap back refers to the use of a single echo on a recorded track. The echo may be placed in a different spatial location in the stereo mix. Normally the echo delay is just large enough to be heard as a discrete echo on careful listening (e.g., on the order of tens of milliseconds). Slap back is very popular in 1950s-style recordings such as ``rockabilly'' tunes.

In summary, slap back can be regarded as a simplification of doubling in which the second voice is kept at a larger, fixed delay relative to the first voice.