1. Sound effect obtained by splitting a signal to two tape machines or networks and introducing a time delay in one of them. Originally achieved by running the same signal on two recorders, one of which was intermittently slowed by an obstruction held against the tape spool. When combined there were alternate cancellations and reinforcements of the two signals. 2. A variable comb filter effect, created by mixing a direct signal with the same signal, passed through a phase shift network.