Flanging
Encyclopedia
Flanging is an audio effect produced by mixing two identical signals together, with 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 resultant 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
dedicated to creating this sound 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.
This flanging is one specific type of phase-shifting
or "phasing". In phasing, the signal is passed through one or more all-pass filter
s 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
.
simultaneously. The playback-head output from these two recorders was then mixed together onto a third recorder. In this form, minute differences in the motor speeds of each machine would result in a phasing effect when the signals were combined. The "flange" effect originated when an engineer would literally put a finger on the flange
, or rim of one of the tape reels so that the machine was slowed down, 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, making the effect sweep back in the other direction.
Alternatively, the track could be recorded to two matching tape decks first, then replayed simultaneously with both decks closely in sync. With this method, slowing down one deck by pressing the tape 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 tape position of the decks move toward being in sync again.
Older recording hardware could suffer from flanging as an undesired side effect when recording very long tracks. As the weight of the tape built up on one reel, the pressure on the capstans could cause flanging during mixdown or dubbing. This was one of the problems 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
.
The development of the classic "flanging" effect is generally attributed to Ken Townsend, an engineer at EMI's
Abbey Road Studio, who devised the process in the spring of 1966. Tired of the laborious process of re-recording dual vocal tracks, John Lennon
asked Townsend if there was some way for the Beatles to get the sound of double-tracked vocals without actually doing the work. After mulling the problem over, Townsend devised Artificial Double Tracking
or "ADT." According to historian Mark Lewisohn
, it was Lennon who actually gave the process the name "flanging". Lennon asked Beatles producer 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-bifurcated sploshing flange with double negative feedback". From that point on, whenever Lennon wanted a Beatles song double-tracked, he would ask for "Ken's flanger". According to Lewisohn, "The Beatles' influence was so vast that 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 completed and released on August 5, 1966, almost every song on the album had been subjected to flanging.
Others have attributed it to 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 "Itchycoo Park
", recorded at Olympic and engineered by Chkiantz's colleague Glyn Johns
.
However there are competing claims for the first recorded use of the technique. One is that the technique was pioneered by the BBC Radiophonic Workshop
, who published their experiments on radio shows such as the Goon Show in freely available journals. ("Flange" was one of many words used out of context on the show to confuse/amuse the audience).
American music industry veterans David S. Gold and Stan Ross, founders of the renowned Gold Star Studios
in Hollywood, claim that they made the first commercial recording to feature the technique - the single "The Big Hurt
" by Toni Fisher
, which was recorded at Gold Star in late 1959 and became a hit in the U.S. in early 1960, rising to #3 on Billboard magazine's
singles chart. Flanging is also heard in the opening of The Ventures
' 1962 cover version of The Tornados
hit "Telstar
", in the context of a simulated rocket launch sound effect
.
The first use of the flanging effect in stereo is credited to producer Eddie Kramer
, who used the effect in the coda of Jimi Hendrix
's "Bold as Love
" (1967). Kramer admitted in an 1990s interview that he read BBC Radiophonic Workshop
technical journals for ideas and circuit diagram
s.
In 1969, the record producer for The Litter
, Warren Kendrick, devised a method to precisely control the flanging effect by placing two 15 IPS (inches per second) stereo Ampex
tape recorders side-by-side. The take-up reel of recorder A and supply reel of recorder 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 was recorded on each channel of the tape, but displaced by approximately 18 inches along the length of the tape. During the recording, a screwdriver
was wedged between the tape 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 back and forth 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" sound effect can also 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.
technology. Solid-state flanging devices fall into two categories: analog and digital. One of the most famous flanger pedals 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.
Note that the original tape-flanging effect sounds a little different from the later electronic and software re-creations. Not only is the tape-flanging signal time-delayed, but the response characteristics at different frequencies of the magnetic tape and tape heads inevitably introduced some 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 amount of 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.
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 in to 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.
Comb filter
In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced spikes, giving the appearance of a comb....
effect: peaks and notches are produced in the resultant 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
Effects unit
Effects units are electronic devices that alter how a musical instrument or other audio source sounds. Some effects subtly "color" a sound, while others transform it dramatically. Effects are used during live performances or in the studio, typically with electric guitar, keyboard and bass...
dedicated to creating this sound 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.
Comparison with phase shifting
Phaser (effect)
A phaser is an audio signal processing technique used to filter a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect...
or "phasing". In phasing, the signal is passed through one or more all-pass filter
All-pass filter
An all-pass filter is a signal processing filter that passes all frequencies equally, but changes the phase relationship between various frequencies. It does this by varying its propagation delay with frequency...
s which have non-linear phase response
Phase response
In signal processing and electrical engineering, phase response is the relationship between the phase of a sinusoidal input and the output signal passing through any device that accepts input and produces an output signal, such as an amplifier or a filter....
, 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
Harmonic series (music)
Pitched musical instruments are often based on an approximate harmonic oscillator such as a string or a column of air, which oscillates at numerous frequencies simultaneously. At these resonant frequencies, waves travel in both directions along the string or air column, reinforcing and canceling...
.
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
White noise
White noise is a random signal with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency...
or similar noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical 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
Comb filter
In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced spikes, giving the appearance of a comb....
.
Origin
The name "flanging" comes from the original method of creation. Originally, a signal would be recorded to two tape machinesTape recorder
An audio tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage...
simultaneously. The playback-head output from these two recorders was then mixed together onto a third recorder. In this form, minute differences in the motor speeds of each machine would result in a phasing effect when the signals were combined. The "flange" effect originated when an engineer would literally put a finger on the flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
, or rim of one of the tape reels so that the machine was slowed down, 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, making the effect sweep back in the other direction.
Alternatively, the track could be recorded to two matching tape decks first, then replayed simultaneously with both decks closely in sync. With this method, slowing down one deck by pressing the tape 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 tape position of the decks move toward being in sync again.
Older recording hardware could suffer from flanging as an undesired side effect when recording very long tracks. As the weight of the tape built up on one reel, the pressure on the capstans could cause flanging during mixdown or dubbing. This was one of the problems faced by studio engineers in the sixties and seventies when recording large concept pieces, as explained by Ian Anderson
Ian Anderson (musician)
Ian Scott Anderson, MBE is a Scottish singer, songwriter and multi-instrumentalist, best known for his work as the leader and flautist of British rock band Jethro Tull.-Early life:...
of Jethro Tull
Jethro Tull (band)
Jethro Tull are a British rock group formed in 1967. Their music is characterised by the vocals, acoustic guitar, and flute playing of Ian Anderson, who has led the band since its founding, and the guitar work of Martin Barre, who has been with the band since 1969.Initially playing blues rock with...
when recounting the studio challenges of recording Thick as a Brick
Thick as a Brick
-Differences between various CD releases:By 2011 the album received three major releases on CD: the first release , the MFSL-release , and the 25th Anniversary Edition . Whereas the first release and the MFSL-release run with identical speed, the 25th Anniversary edition runs 0.5% slower...
.
The development of the classic "flanging" effect is generally attributed to Ken Townsend, an engineer at EMI's
EMI
The EMI Group, also known as EMI Music or simply EMI, is a multinational music company headquartered in London, United Kingdom. It is the fourth-largest business group and family of record labels in the recording industry and one of the "big four" record companies. EMI Group also has a major...
Abbey Road Studio, who devised the process in the spring of 1966. Tired of the laborious process of re-recording dual vocal tracks, John Lennon
John Lennon
John Winston Lennon, MBE was an English musician and singer-songwriter who rose to worldwide fame as one of the founding members of The Beatles, one of the most commercially successful and critically acclaimed acts in the history of popular music...
asked Townsend if there was some way for the Beatles to get the sound of double-tracked vocals without actually doing the work. After mulling the problem over, Townsend devised Artificial Double Tracking
Automatic double tracking
Automatic double-tracking or artificial double-tracking was an analogue recording technique designed to enhance the sound of voices or instruments during the recording process. It used tape delay to create a delayed copy of an audio signal which was then combined with the original...
or "ADT." According to historian Mark Lewisohn
Mark Lewisohn
Mark Lewisohn is an English author and historian, regarded as the world's leading authority on the English rock band The Beatles.-The Beatles and related subjects:...
, it was Lennon who actually gave the process the name "flanging". Lennon asked Beatles producer George Martin
George Martin
Sir George Henry Martin CBE is an English record producer, arranger, composer and musician. He is sometimes referred to as "the Fifth Beatle"— a title that he often describes as "nonsense," but the fact remains that he served as producer on all but one of The Beatles' original albums...
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-bifurcated sploshing flange with double negative feedback". From that point on, whenever Lennon wanted a Beatles song double-tracked, he would ask for "Ken's flanger". According to Lewisohn, "The Beatles' influence was so vast that 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
Revolver (album)
Revolver is the seventh studio album by the English rock group The Beatles, released on 5 August 1966 on the Parlophone label and produced by George Martin. Many of the tracks on Revolver are marked by an electric guitar-rock sound, in contrast with their previous LP, the folk rock inspired Rubber...
, which was recorded on April 6, 1966. When Revolver was completed and released on August 5, 1966, almost every song on the album had been subjected to flanging.
Others have attributed it to George Chkiantz
George Chkiantz
George Chkiantz is a recording engineer based in London who has been responsible for the engineering on a number of well-known albums, many of which are considered classics, owing in part to the high quality of the recordings....
, an engineer employed at Olympic Studios
Olympic Studios
Olympic Studios was a renowned independent commercial recording studio located at 117 Church Road, Barnes, South West London, England. The studio is best known for the huge number of famous rock and pop recordings made there from the late 1960s onward....
in Barnes, London
London
London is the capital city of :England and the :United Kingdom, the largest metropolitan area in the United Kingdom, and the largest urban zone in the European Union by most measures. Located on the River Thames, London has been a major settlement for two millennia, its history going back to its...
. One of the first instances of the sound being used on a commercial pop recording was The Small Faces
The Small Faces
The Small Faces were an English rock and roll band from East London, heavily influenced by American rhythm and blues. The group was founded in 1965 by members Steve Marriott, Ronnie Lane, Kenney Jones, and Jimmy Winston, although by 1966 Winston was replaced by Ian McLagan as the band's...
' 1967 single "Itchycoo Park
Itchycoo Park
"Itchycoo Park" is a psychedelic pop song written by Steve Marriott and Ronnie Lane, first recorded by their group, the Small Faces. The song reached number three in the UK Singles Chart, 1967.-Song profile:...
", recorded at Olympic and engineered by Chkiantz's colleague Glyn Johns
Glyn Johns
Glyn Johns is a musician, recording engineer and record producer.-Career:He has worked with such artists as Bob Dylan, The Beatles, The Easybeats, The Band, The Rolling Stones, The Who, Led Zeppelin, Eagles, Eric Clapton, The Clash, The Steve Miller Band, Small Faces, Spooky Tooth, The Ozark...
.
However there are competing claims for the first recorded use of the technique. One is that the technique was pioneered by the BBC Radiophonic Workshop
BBC Radiophonic Workshop
The BBC Radiophonic Workshop, one of the sound effects units of the BBC, was created in 1958 to produce effects and new music for radio, and was closed in March 1998, although much of its traditional work had already been outsourced by 1995. It was based in the BBC's Maida Vale Studios in Delaware...
, who published their experiments on radio shows such as the Goon Show in freely available journals. ("Flange" was one of many words used out of context on the show to confuse/amuse the audience).
American music industry veterans David S. Gold and Stan Ross, founders of the renowned Gold Star Studios
Gold Star Studios
Gold Star Studios was a major independent recording studio located in Los Angeles, California, United States. For more than thirty years, from 1950 to 1984, Gold Star was one of the most influential and successful commercial recording studios in the world....
in Hollywood, claim that they made the first commercial recording to feature the technique - the single "The Big Hurt
The Big Hurt (song)
"The Big Hurt" is a pop song, that was a hit Toni Fisher in 1959. The song was written by her husband, Wayne Shanklin. The song went to No. 3 on the Billboard Hot 100 music chart in the United States...
" by Toni Fisher
Toni Fisher
Toni Fisher was an American pop singer. She was known for her recordings of "The Big Hurt", "West of the Wall", "Maybe ," and "Why Can't The Dark Leave Me Alone".-Biography:...
, which was recorded at Gold Star in late 1959 and became a hit in the U.S. in early 1960, rising to #3 on Billboard magazine's
Billboard (magazine)
Billboard is a weekly American magazine devoted to the music industry, and is one of the oldest trade magazines in the world. It maintains several internationally recognized music charts that track the most popular songs and albums in various categories on a weekly basis...
singles chart. Flanging is also heard in the opening of The Ventures
The Ventures
The Ventures is an American instrumental rock band formed in 1958 in Tacoma, Washington. Founded by Don Wilson and Bob Bogle, the group in its various incarnations has had an enduring impact on the development of music worldwide. With over 100 million records sold, the group is the best-selling...
' 1962 cover version of The Tornados
The Tornados
The Tornados were an English instrumental group of the 1960s that acted as backing group for many of record producer Joe Meek's productions and also for singer Billy Fury. They enjoyed several chart hits in their own right, including the UK and U.S. Number One "Telstar" , the first U.S...
hit "Telstar
Telstar (song)
"Telstar" is a 1962 instrumental record performed by The Tornados. It was the first single by a British band to reach number one on the U.S. Billboard Hot 100, and was also a number one hit in the UK. The record was named after the AT&T communications satellite Telstar, which went into orbit in...
", in the context of a simulated rocket launch sound effect
Sound effect
For the album by The Jam, see Sound Affects.Sound effects or audio effects are artificially created or enhanced sounds, or sound processes used to emphasize artistic or other content of films, television shows, live performance, animation, video games, music, or other media...
.
The first use of the flanging effect in stereo is credited to producer Eddie Kramer
Eddie Kramer
Edwin H. Kramer is an audio engineer and producer who has worked with, among others, Led Zeppelin, Triumph, Kiss , Jimi Hendrix, The Beatles, The Rolling Stones, David Bowie, Spooky Tooth, Peter Frampton, Curtis Mayfield, Santana, Anthrax, Carly Simon, Loudness, and Robin Trower.-1960s:Eddie...
, who used the effect in the coda of Jimi Hendrix
Jimi Hendrix
James Marshall "Jimi" Hendrix was an American guitarist and singer-songwriter...
's "Bold as Love
Bold as Love (song)
"Bold as Love" is a song by Jimi Hendrix, the final song and title track of the Jimi Hendrix Experience's 1967 album Axis: Bold as Love.-Recording:...
" (1967). Kramer admitted in an 1990s interview that he read BBC Radiophonic Workshop
BBC Radiophonic Workshop
The BBC Radiophonic Workshop, one of the sound effects units of the BBC, was created in 1958 to produce effects and new music for radio, and was closed in March 1998, although much of its traditional work had already been outsourced by 1995. It was based in the BBC's Maida Vale Studios in Delaware...
technical journals for ideas and circuit diagram
Circuit diagram
A circuit diagram is a simplified conventional graphical representation of an electrical circuit...
s.
The Litter
The Litter was an American psychedelic and garage rock band, formed in 1966 in Minneapolis. They are best remembered for their 1967 debut single "Action Woman." The group recorded an album in 1972 but would re-unite in 1990, 1992, and again in 1998, when they recorded a new studio album consisting...
, Warren Kendrick, devised a method to precisely control the flanging effect by placing two 15 IPS (inches per second) stereo Ampex
Ampex
Ampex is an American electronics company founded in 1944 by Alexander M. Poniatoff. The name AMPEX is an acronym, created by its founder, which stands for Alexander M. Poniatoff Excellence...
tape recorders side-by-side. The take-up reel of recorder A and supply reel of recorder 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 was recorded on each channel of the tape, but displaced by approximately 18 inches along the length of the tape. During the recording, a screwdriver
Screwdriver
A screwdriver is a tool for driving screws and often rotating other machine elements with the mating drive system. The screwdriver is made up of a head or tip, which engages with a screw, a mechanism to apply torque by rotating the tip, and some way to position and support the screwdriver...
was wedged between the tape 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 back and forth 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" sound effect can also 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.
Artificial flanging
In the 1970s, advances in solid-state electronics made the flanging effect possible using integrated circuitIntegrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
technology. Solid-state flanging devices fall into two categories: analog and digital. One of the most famous flanger pedals is the Electro Harmonix Electric Mistress. The flanging effect in most newer digital flangers relies on DSP
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
technology. Flanging can also be accomplished using computer software.
Note that the original tape-flanging effect sounds a little different from the later electronic and software re-creations. Not only is the tape-flanging signal time-delayed, but the response characteristics at different frequencies of the magnetic tape and tape heads inevitably introduced some phase
Phase (waves)
Phase in waves is the fraction of a wave cycle which has elapsed relative to an arbitrary point.-Formula:The phase of an oscillation or wave refers to a sinusoidal function such as the following:...
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 amount of 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 toneShepard tone
A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually...
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 in to 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.