A type of delay line which uses an endless loop of magnetic recording tape (or other magnetic media) to produce the delay. Typically, a loop of tape passes across a record head, where the source material is recorded onto the tape; then as the tape progresses through the mechanism, at some point later it passes a playback head where the recorded signal is reproduced. Some of the playback signal is then fed back to the record head, mixed with the source material, to produce a repeating echo that diminishes each time it repeats.