Flanging

Part of the output signal is usually fed back to the input (a re-circulating delay line), producing a resonance effect that further enhances the intensity of the peaks and troughs.

The finished music track is recorded simultaneously to two matching tape machines, then replayed with both decks in sync.

The engineer slows down one playback recorder by lightly pressing a finger on the flange (rim) of the supply reel.

The drainpipe or subtle swoosh effect sweeps in one direction, and the playback of that recorder remains slightly behind the other when the finger is removed.

The Beatles' producer George Martin disputed this reel flange source, attributing the term to himself and John Lennon instead.

[1][2] Despite claims over who originated flanging, Les Paul discovered the effect in the late 1940s and 1950s; however, he did most of his early phasing experiments with acetate disks on variable-speed record players.

[5] Further development of the classic effect is attributed to Ken Townsend, an engineer at EMI's Abbey Road Studio, who devised a process in the spring of 1966.

From that point, when Lennon wanted ADT he would ask for his voice to be flanged, or call out for "Ken's flanger".

The first stereo flanging is credited to producer Eddie Kramer, in the coda of Jimi Hendrix's "Bold as Love" (1967).

[9][10][11][12] A similar "jet plane-like" effect can occur naturally in long distance shortwave radio music broadcasts.

The Eventide Instant Flanger from 1975 is an early example of a studio device that was able to successfully simulate tape flanging using bucket-brigades to create the audio delay.

Thus, while the peaks and troughs of the comb filter are more or less in a linear harmonic series, there is a significant non-linear behaviour too, causing the timbre of tape-flanging to sound more like a combination of what came to be known as flanging and phasing.

Also known as "infinite flanging", this sonic illusion is similar to the Shepard tone effect, and is equivalent to an auditory "barber pole".