Phasing

Phasing is an audio effect in which a sound combines with a replica of itself to produce a comb filter effect. This effect can be heard on numerous psychedelic records of the 1960s, notably Itchycoo Park by the Small Faces. A phaser is an electronic device used to produce this effect. It was originally produced by simply copying the sound onto two analogue tape decks and mixing them together with one tape running slightly faster than the other, so that one copy of the sound would overtake the other, resulting in a rising then falling effect caused by wave interference. See also flanging, wave interference. The compositional technique phasing discovered by composer Steve Reich is that while the same part is played on two instruments, one instrumentalist keeps playing in steady tempo, while the other gradually moves ahead until it becomes back in phase (the rhythmic equivalent of cycling through the phase of two waveforms). Francis Grasso is credited with originating phasing as a DJ technique, playing two copies of the same record from the same point at the same time so as to create a phase effect.