A signal processor often identified as the one that creates a “jet taking off” whoosh. What’s going on behind the panel is that a copy of the input signal is delayed by a very small amount (longer than a chorus effect; shorter than an echo effect) and mixed in with the original. When the delay is constant, the result is a “comb filter” where certain harmonics are cancelled out as they are mixed back on top of themselves out of phase. When the delay is varied over time, you get swooshes and sweeps.
The effect was originally created by playing two tape reels of the same song, starting them in time with each other, and dragging your finger on the flange of one of the tape reels to delay it.« Back to Glossary Index