Flanging
Flanging is an audio effect that occurs when two identical signals are played together almost simultaneously, with one signal being in opposite phase to the other and their outputs mixed together. A tiny and gradually shifting delay between the signals, usually smaller than 10 ms (milliseconds), gives a 'comb filter' effect that changes over time. A flanger is a device dedicated to creating this sound effect.
The effect was given its name by John Lennon in 1966. However the term used by The Beatles is now known to have specifically referred to flanging's 'parent' process, automatic double tracking (ADT), which was invented in April 1966 by Abbey Road engineeer Ken Townshend. ADT used linked tape recorders to automatically creating a synchronised duplicate of a lead vocal or an instrument. It was created largely at the instigation of Lennon, who hated the tedium of having to 'manually' record duplicate vocals for Beatles recordings -- the only way this effect could be achieved before ADT. The Beatles were delighted with Townshend's invention and used it routinely thereafter; it was the famously non-technical Lennon who is said to have nick-named the ADT process Ken's flanger or flanging (for reasons outlined below).
The name flanging comes from the original method of creation, which involved playing the same recording on two synchronized tape recorders with the output of one machine out of phase as above, and then mixing the two output signals together. As long as the machines are perfectly synchronized, the result will be silence, as the signals will be cancelling each other out. Given the near-impossibility of keeping two analog tape decks perfectly in sync, however, this silence is only be achieveable for a split second before the signals slip slowly out of sync again. If the operator places his/her finger on the flange (that is to say, the rim) of one of the tape reels, that machine can be made to slow down, slipping out of sync by tiny degrees. A listener will hear the familiar "drainpipe" swooping effect as shifting sum-and-difference harmonics are created.
The classic flanging effect is believed to have been first perfected during 1966 by George Chkiantz, an engineer employed at Olympic Studios in Barnes, London. One of the first instances of the sound being used on a commercial pop recording was the Small Faces' 1967 single Itchykoo Park, recorded at Olympic and engineered by Chkiantz's colleague Glyn Johns.
If the frequency response of this effect is plotted on a graph, the trace resembles a comb, and so is called a comb filter. Once the operator takes his/her finger off, that player will speed up until its tachometer is back in phase with the master, and as this happens, the flanging effect will be repeated, with the harmonics swooping gradually higher until both signals pass momentarily through the silent perfect sync point again. It is often aesthetically better not to let the two tapes reach this point, but to start the reel-slowing again just before they get back into sync.
In the 1970s, advances in solid state electronics made the flanging effect possible using integrated circuit technology. Solid state flanging devices fall into two categories: analog and digital. The flanging effect in most newer digital flangers relies on DSP technology. Flanging can also be accomplished using computer software. Even today, though, many studio practitioners prefer the sound of analog tape flanging, finding the serendipitous nature of human intervention more interesting than the clinical perfection created by purely electronic means. Tape flanging requires bulky hardware and takes quite a knack to get right, but some consider the results to be well worth the time and effort.
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