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)