|This article needs additional citations for verification. (May 2010)|
Flanging // is an audio effect produced by mixing two identical signals together, one signal delayed by a small and gradually changing period, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resulting frequency spectrum, related to each other in a linear harmonic series. Varying the time delay causes these to sweep up and down the frequency spectrum. A flanger is an effects unit that creates this effect.
Part of the output signal is usually fed back to the input (a "re-circulating delay line"), producing a resonance effect which further enhances the intensity of the peaks and troughs. The phase of the fed-back signal is sometimes inverted, producing another variation on the flanging sound.
A short sample followed by two flanging versions.
|Problems playing this file? See media help.|
The name "flanging" comes from the original method. Originally, a signal would be recorded to two tape machines simultaneously. The playback-head output from the recorders was then mixed to a third recorder. In this form, minute differences in the motor speeds of each resulted in a phasing effect when signals were combined. The "flange" effect originated when an engineer put a finger on the flange, or rim, of one of the tape reels so the machine was slowed, slipping out of sync by tiny degrees. A listener would hear a "drainpipe" sweeping effect as shifting sum-and-difference harmonics were created. When the operator removed his finger the tape sped up again, sweeping the effect in the other direction. Beatles' producer George Martin has disputed this "reel flange" source, instead attributing the term to John Lennon (see Martin's account below).
Alternatively, the track could be recorded to two matching tape decks, then replayed simultaneously with both decks in sync. With this method, slowing one deck by pressing the reel flange would "sweep" the flange effect in one direction, but when released the playback of that deck would remain slightly behind the other, and the effect would not sweep back. Instead, pressing the flange of the other deck would sweep the effect back in the other direction as the decks moved towards being in sync again.
Older recording hardware could suffer flanging as a side effect when recording long tracks. As the weight of the tape built on one reel, the pressure on the capstans caused flanging in mixdown or dubbing. This was a problem faced by studio engineers in the sixties and seventies when recording large concept pieces, as explained by Ian Anderson of Jethro Tull when recounting the studio challenges of recording Thick as a Brick.
Development of the classic effect is attributed to Ken Townsend, an engineer at EMI's Abbey Road Studio, who devised the process in spring 1966. Tired of laboriously re-recordinging dual vocal tracks, John Lennon asked Townsend if there was some way for the Beatles to get the sound of double-tracked vocals without doing the work. Townsend devised Artificial Double Tracking or ADT. According to historian Mark Lewisohn, Lennon who gave the name "flanging". Lennon asked George Martin to explain how ADT worked, and Martin answered with the nonsense explanation "Now listen, it's very simple. We take the original image and we split it through a double vibrocated sploshing flange with double negative feedback". Lennon thought Martin was joking. Martin replied, "Well, let's flange it again and see". From that point, when Lennon wanted ADT he would ask for his voice to be flanged, or call out for "Ken's flanger". According to Lewisohn, the Beatles' influence meant the term "flanging" is still in use today, more than 20 years on. The first Beatles track to feature flanging was "Tomorrow Never Knows" from Revolver, which was recorded on April 6, 1966. When Revolver was released on August 5, 1966, almost every song had been subjected to flanging.
Others have attributed it to George Chkiantz, an engineer at Olympic Studios in Barnes, London. One of the first instances on a pop recording was The Small Faces' 1967 single "Itchycoo Park", recorded at Olympic and engineered by Chkiantz's colleague Glyn Johns.
listen to the tape flanging effect on the 1967 single.
|Problems playing this file? See media help.|
American music industry veterans David S. Gold and Stan Ross, founders of Gold Star Studios in Hollywood, claim they made the first commercial recording — the single "The Big Hurt" by Toni Fisher - at Gold Star in late 1959 and a hit in the United States in early 1960, rising to #3 on Billboard magazine's singles chart. Flanging is also heard in the opening of The Ventures' 1962 cover of The Tornados' "Telstar", in a rocket launch sound effect.
The first stereo flanging is credited to producer Eddie Kramer, in the coda of Jimi Hendrix's "Bold as Love" (1967). Kramer said in the 1990s that he read BBC Radiophonic Workshop journals for ideas and circuit diagrams.
In 1968, the record producer for The Litter, Warren Kendrick, devised a method to control flanging by placing two 15ips (inches per second) stereo Ampex tape recorders side by side. The take-up reel of recorder A and supply reel of B were disabled, as were channel 2 of recorder A, channel 1 of recorder B and the erase head of recorder B. The tape was fed left-to-right across both recorders and an identical signal recorded on each channel of the tape, but displaced by approximately 18 inches along the length of the tape. During recording, a screwdriver was wedged between the recorders to make the tape run "uphill" and "downhill." The same configuration was employed during the playback/mixdown to a third recorder. The screwdriver was moved to cause the two signals to diverge, then converge. The latter technique permits zero point flanging; i.e., the lagging signal crosses over the leading signal and the signals change places.
A similar "jet plane-like" effect can occur naturally in long distance shortwave radio music broadcasts. In this case the varying delays are caused by varying radio wave propagation times and multipath radio interference.
In the 1970s, advances in solid-state electronics made flanging possible using integrated circuit technology. Solid-state flanging devices fall into two categories: analog and digital. One flanger pedal is the Electro Harmonix Electric Mistress. The flanging effect in most newer digital flangers relies on DSP technology. Flanging can also be accomplished using computer software.
The original tape-flanging effect sounds a little different from electronic and software recreations. Not only is the tape-flanging signal time-delayed, but response characteristics at different frequencies of the tape and tape heads introduced phase shifts into the signals as well. 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.
"Barber pole" flanging
Also known as "infinite flanging", this sonic illusion is similar to the Shepard tone effect, and is equivalent to an auditory "barber pole". The sweep of the flanged sound seems to move in only one direction ("up" or "down") infinitely, instead of sweeping back-and-forth. While Shepard tones are created by generating a cascade of tones, fading in and out while sweeping the pitch either up or down, barber pole flanging uses a cascade of multiple delay lines, fading each one into the mix and fading it out as it sweeps to the delay time limit. The effect is available on various hardware and software effect systems.
Comparison with phase shifting
This flanging is one specific type of phase-shifting or "phasing". In phasing, the signal is passed through one or more all-pass filters which have non-linear phase response, and then added back to the original signal. This results in constructive and destructive interference that varies with frequency, giving a series of peaks and troughs in the frequency response of the system. In general, the position of these peaks and troughs do not occur in a harmonic series.
In contrast, flanging relies on adding the signal to a uniform time-delayed copy of itself, which results in an output signal with peaks and troughs which are in a harmonic series. Extending the comb analogy, flanging yields a comb filter with regularly spaced teeth, whereas phasing results in a comb filter with irregularly spaced teeth.
In both phasing and flanging, the characteristics (phase response and time delay, respectively) are generally varied in time, leading to an audible sweeping effect.
To the ear, flanging and phasing sound similar, yet they are recognizable as distinct colorations.
Commonly, flanging is referred to as having a "jet plane-like" characteristic. In order for the comb filter effect to be audible, the spectral content of the program material must be full enough within the frequency range of this moving comb filter to reveal the filter’s effect. It is more apparent when it is applied to material with a rich harmonic content, and is most obvious when applied to a white noise or similar noise signal.
If the frequency response of this effect is plotted on a graph, the trace resembles a comb, and so is called a comb filter.
- Martin, George; Pearson, William (1994). Summer of Love: The Making of Sgt Pepper. London: Pan Books. p. 82. ISBN 0-330-34210-X.
- Lewisohn, Mark. The Beatles: Recording Sessions (New York: Harmony Books, 1988), page 70.
- Hodgson, Jay (2010). Understanding Records, p.142. ISBN 978-1-4411-5607-5. Interludes between chorus and verse at 0:50-1:07, 1:40-2:05, and 2:20-2:46.
- Diagram by Warren Kendrick - 'K-Tel Reissue CD 10002 (1991)'
- "The Sonic Barber Pole: Shepard's Scale". at cycleback.com.
- Budde, Christian. Barberpole Flanger at kvraudio.com]
- "audio software by oli larkin". Olilarkin.co.uk. Retrieved 2012-08-13.