Phasing is a compositional technique in which the same part (a repetitive phrase) is played on two musical instruments, in steady but not identical tempi. Thus, the two instruments gradually shift out of unison, creating first a slight echo as one instrument plays a little behind the other, then a doubling with each note heard twice, then a complex ringing effect, and eventually coming back through doubling and echo into unison. (More from Wikipedia)
Another fun effect is running the same or similar musical sections slightly out of synch; it is variously described as phasing and flanging. The latter term was reportedly coined by John Lennon and is still in use today; it refers to sound effects caused by the manual or accidental slowing down of tape in a take-up reel, though the effect can be created electronically as well. The Wikipedia article on flanging describes it this way: “As an audio effect, a listener hears a ‘drainpipe’ or ‘swoosh’ or ‘jet plane’ sweeping effect as shifting sum-and-difference harmonics are created analogous to use of a variable notch filter.” One of the earliest uses of phasing in rock music is the 1967 hit song by Small Faces, “Itchycoo Park”.
(July 2015)
