Parallel compression
Encyclopedia
Parallel compression, also known as New York compression, is a dynamic range compression technique used in sound recording
and mixing
. Parallel compression, a form of upward compression, is achieved by mixing an unprocessed 'dry', or lightly compressed signal with a heavily compressed version of the same signal. Rather than bringing down the highest peaks for the purpose of dynamic range
reduction, it reduces the dynamic range by bringing up the softest sounds, adding audible detail. It is most often used on stereo percussion buses in recording and mixdown, on electric bass
, and on vocals in recording mixes and live concert mixes.
noise reduction, introduced in 1965, contained parallel buses with heavy compression on one of them, the two mixed together in a flexible ratio. In October 1977, an article by Mike Bevelle was published in Studio Sound magazine, describing the technique as applied to studio recordings. Bevelle called it "side-chain" compression, though that term made for confusion with the side-chain compression technique which uses an external "key" or "side chain" signal to determine compression on a target signal. Bevelle's article, entitled "Compressors and Limiters", was reprinted in the same magazine in June 1988. Bob Katz
coined the term "parallel compression", and has described it as an implementation of "upward compression", the increase in audibility of softer passages. Studio engineers in New York City became known for reliance on the technique, and it picked up the name "New York compression".
In an audio mix using an analog mixing console
and analog compressors, parallel compression is achieved by sending a monophonic or stereo signal two or more directions and then summing the multiple pathways, mixing them together by ear to achieve the desired effect. One pathway is straight to the summing mixer, other pathways go through mono or stereo compressors, set aggressively for high-ratio gain reduction. The compressed signals are brought back to the summing mixer and blended in with the straight signal.
If digital components are being used, latency
must be taken into account. If the normal analog method is used for a digital compressor, the signals traveling through the parallel pathways will arrive at the summing mixer at slightly different times, creating unpleasant comb-filtering and phasing effects. The digital compressor pathway takes a little more time to process the sound—on the order of 0.3 to 3 milliseconds longer. Instead, the two pathways must both have the same number of processing stages: the "straight" pathway is assigned a compression stage which is not given an aggressively high ratio. In this case, the two signals both go through compression stages, and both pathways are delayed the same amount of time, but one is set to do no dynamic range compression, or to do very little, and the other is set for high amounts of gain reduction.
The method can be used artistically to "fatten" or "beef up" a mix, by careful setting of attack and release times on the compressor. These settings may be adjusted further until the compressor causes the signal to "pump" or "breathe" in tempo
with the song, adding its own character to the sound. Unusually extreme implementations have been achieved by studio mix engineers such as New York-based Michael Brauer
who uses five parallel compressors, adjusted individually for timbral
and tonal variations, mixed and blended to taste, to achieve his target sound on vocals for The Rolling Stones
, Aerosmith
, Bob Dylan
, KT Tunstall
and Coldplay
. Mix engineer Anthony "Rollmottle" Puglisi uses parallel compression applied conservatively across the entire mix, especially in dance-oriented electronic music: "it gives a track that extra oomph and power (not just make it louder—there's a difference) through quieter portions of the jam without resorting to one of those horrific 'maximizer' plugins that squeeze the dynamics right out of your song." While parallel compression is widely utilized in electronic dance music, "side-chain" compression is the technique popularly used to give a synth lead or other melodic element the pulsating quality ubiquitous in the genre. One or more tracks may be side-chained to the kick, thereby compressing them only when the beat occurs.
Sound recording and reproduction
Sound recording and reproduction is an electrical or mechanical inscription and re-creation of sound waves, such as spoken voice, singing, instrumental music, or sound effects. The two main classes of sound recording technology are analog recording and digital recording...
and mixing
Audio mixing (recorded music)
In audio recording, audio mixing is the process by which multiple recorded sounds are combined into one or more channels, most commonly two-channel stereo. In the process, the source signals' level, frequency content, dynamics, and panoramic position are manipulated and effects such as reverb may...
. Parallel compression, a form of upward compression, is achieved by mixing an unprocessed 'dry', or lightly compressed signal with a heavily compressed version of the same signal. Rather than bringing down the highest peaks for the purpose of dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
reduction, it reduces the dynamic range by bringing up the softest sounds, adding audible detail. It is most often used on stereo percussion buses in recording and mixdown, on electric bass
Bass guitar
The bass guitar is a stringed instrument played primarily with the fingers or thumb , or by using a pick....
, and on vocals in recording mixes and live concert mixes.
History
The internal circuitry of Dolby ADolby Stereo
Dolby Stereo, is the trade mark that Dolby Laboratories used for the various analogue stereo cinema sound formats that they produced.Two basic systems used this name. The first was the 'Dolby SVA' system used with optical soundtracks on 35mm film...
noise reduction, introduced in 1965, contained parallel buses with heavy compression on one of them, the two mixed together in a flexible ratio. In October 1977, an article by Mike Bevelle was published in Studio Sound magazine, describing the technique as applied to studio recordings. Bevelle called it "side-chain" compression, though that term made for confusion with the side-chain compression technique which uses an external "key" or "side chain" signal to determine compression on a target signal. Bevelle's article, entitled "Compressors and Limiters", was reprinted in the same magazine in June 1988. Bob Katz
Bob Katz
Bob Katz is an audio mastering engineer who is known for his book on audio mastering. Katz has mastered three Grammy award-winning albums and one nominated album. He has received acclaim from audiophiles and his book on mastering has received acclaim, and some reviewers consider it the "definitive...
coined the term "parallel compression", and has described it as an implementation of "upward compression", the increase in audibility of softer passages. Studio engineers in New York City became known for reliance on the technique, and it picked up the name "New York compression".
Use
The human ear is sensitive to loud sounds being suddenly reduced in volume, but less so to soft sounds being increased in volume—parallel compression takes advantage of this difference. Unlike normal limiting and downward compression, fast transients in music are retained in parallel compression, preserving the "feel" and immediacy of a live performance. Because the method is less audible to the human ear, the compressor can be set aggressively, with high ratios for strong effect.In an audio mix using an analog mixing console
Mixing console
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, or mixer is an electronic device for combining , routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer...
and analog compressors, parallel compression is achieved by sending a monophonic or stereo signal two or more directions and then summing the multiple pathways, mixing them together by ear to achieve the desired effect. One pathway is straight to the summing mixer, other pathways go through mono or stereo compressors, set aggressively for high-ratio gain reduction. The compressed signals are brought back to the summing mixer and blended in with the straight signal.
If digital components are being used, latency
Latency (audio)
Latency refers to a short period of delay between when an audio signal enters and when it emerges from a system...
must be taken into account. If the normal analog method is used for a digital compressor, the signals traveling through the parallel pathways will arrive at the summing mixer at slightly different times, creating unpleasant comb-filtering and phasing effects. The digital compressor pathway takes a little more time to process the sound—on the order of 0.3 to 3 milliseconds longer. Instead, the two pathways must both have the same number of processing stages: the "straight" pathway is assigned a compression stage which is not given an aggressively high ratio. In this case, the two signals both go through compression stages, and both pathways are delayed the same amount of time, but one is set to do no dynamic range compression, or to do very little, and the other is set for high amounts of gain reduction.
The method can be used artistically to "fatten" or "beef up" a mix, by careful setting of attack and release times on the compressor. These settings may be adjusted further until the compressor causes the signal to "pump" or "breathe" in tempo
Tempo
In musical terminology, tempo is the speed or pace of a given piece. Tempo is a crucial element of any musical composition, as it can affect the mood and difficulty of a piece.-Measuring tempo:...
with the song, adding its own character to the sound. Unusually extreme implementations have been achieved by studio mix engineers such as New York-based Michael Brauer
Michael Brauer
Michael Brauer is a New York-based mix engineer whose credits encompass a wide range of genres, and include The Rolling Stones, Bob Dylan, Paul McCartney, Coldplay, John Mayer, Ash, My Morning Jacket, Ben Folds, Dream Theater, The New Radicals, Change, Fountains of Wayne, David Poe, Wilco, Alpha...
who uses five parallel compressors, adjusted individually for timbral
Timbre
In music, timbre is the quality of a musical note or sound or tone that distinguishes different types of sound production, such as voices and musical instruments, such as string instruments, wind instruments, and percussion instruments. The physical characteristics of sound that determine the...
and tonal variations, mixed and blended to taste, to achieve his target sound on vocals for The Rolling Stones
The Rolling Stones
The Rolling Stones are an English rock band, formed in London in April 1962 by Brian Jones , Ian Stewart , Mick Jagger , and Keith Richards . Bassist Bill Wyman and drummer Charlie Watts completed the early line-up...
, Aerosmith
Aerosmith
Aerosmith is an American rock band, sometimes referred to as "The Bad Boys from Boston" and "America's Greatest Rock and Roll Band". Their style, which is rooted in blues-based hard rock, has come to also incorporate elements of pop, heavy metal, and rhythm and blues, and has inspired many...
, Bob Dylan
Bob Dylan
Bob Dylan is an American singer-songwriter, musician, poet, film director and painter. He has been a major and profoundly influential figure in popular music and culture for five decades. Much of his most celebrated work dates from the 1960s when he was an informal chronicler and a seemingly...
, KT Tunstall
KT Tunstall
Kate Victoria "KT" Tunstall is a Scottish singer-songwriter and guitarist from St Andrews, Scotland. She broke into the public eye with a 2004 live solo performance of her song "Black Horse and the Cherry Tree" on Later... with Jools Holland...
and Coldplay
Coldplay
Coldplay are a British alternative rock band formed in 1996 by lead vocalist Chris Martin and lead guitarist Jonny Buckland at University College London. After they formed Pectoralz, Guy Berryman joined the group as a bassist and they changed their name to Starfish. Will Champion joined as a...
. Mix engineer Anthony "Rollmottle" Puglisi uses parallel compression applied conservatively across the entire mix, especially in dance-oriented electronic music: "it gives a track that extra oomph and power (not just make it louder—there's a difference) through quieter portions of the jam without resorting to one of those horrific 'maximizer' plugins that squeeze the dynamics right out of your song." While parallel compression is widely utilized in electronic dance music, "side-chain" compression is the technique popularly used to give a synth lead or other melodic element the pulsating quality ubiquitous in the genre. One or more tracks may be side-chained to the kick, thereby compressing them only when the beat occurs.