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{{shortShort description|ChangingChange of a sound over time}}
{{Redirect|Sustain}}
{{Broader|Envelope (waves)}}
{{Use American English|date=June 2022}}
 
In [[sound]] and [[music]], an '''envelope''' describes how a sound changes over time. ItFor example, a piano key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero. An envelope may relate to elements such as [[amplitude]] (volume), frequency (with the use of [[Voltage-controlled filter|filters]] (frequencies) or [[Pitch (music)|pitch]]. For example, a [[piano]] key, when struck and held, creates a near-immediate initial sound which gradually decreases in volume to zero.
 
'''Envelope generators''', which allow users to control the different stages of a sound, are common features of [[synthesizer]]s, [[Sampler (musical instrument)|samplers]], and other [[electronic musical instrument]]s. The most common form of envelope generator is controlled with four parameters: '''attack''', '''decay''', '''sustain''' and '''release''' ('''ADSR''').
 
== DevelopmentEnvelope generators ==
[[File:Korg ARP Odyssey ADSR 0113.jpg|thumb|right|The ADSR envelope controls of a [[ARP Odyssey|Korg ARP Odyssey]] synthesiser]]▼
The Hammond [[Novachord]] in 1938 used an early implementation of an ADSR envelope. A seven-position rotary knob selects preset ADS parameter for all 72 notes; a pedal controls the release.<ref name="cirocco2006">{{cite web |url=http://www.discretesynthesizers.com/nova/intro.htm |title=The Novachord Restoration Project |last=Cirocco |first=Phil |year=2006 |publisher=Cirocco Modular Synthesizers}}</ref>
 
=== Development ===
The envelope generator was created by the American engineer [[Robert Moog]] in the 1960s. While experimenting with the first [[Moog synthesizer]]s, composer [[Herbert Deutsch]] suggested Moog find a way to articulate the instrument so notes did not simply trigger on and off. Moog wired a [[doorbell]] button to the synthesizer and used a [[capacitor]] to store and slowly release [[voltage]] produced from hitting a key. He refined the design to remove the need to push a separate button with every keypress, with two switches on every key: one to produce the control voltage determining pitch and the other to trigger the envelope generator. The envelope generator became a standard feature of synthesizers.<ref name=":2">{{Cite book |title=Analog Days: The Invention and Impact of the Moog Synthesizer |last1=Pinch |first1=Trevor |last2=Trocco |first2=Frank |publisher=[[Harvard University Press]] |year=2004 |isbn=978-0-674-01617-0 |pages=[https://archive.org/details/analogdaysinvent00trev/page/43 43] |url=https://archive.org/details/analogdaysinvent00trev/page/43}}</ref>▼
▲[[File:Korg ARP Odyssey ADSR 0113.jpg|thumb|right|The ADSR envelope controls of a [[ARP Odyssey|Korg ARP Odyssey]] synthesisersynthesizer]]
▲The envelope generator was created by the American engineer [[Robert Moog]] in, the 1960s.creator While experimenting withof the first [[Moog synthesizer]]s, in the 1960s. The composer [[Herbert Deutsch]] suggested Moog find a way to articulate thehis instrumentsynthesizer so notes did not simply trigger on and off. Moog wired a [[doorbell]] button to the synthesizer and used a [[capacitor]] to store and slowly release [[voltage]] produced from hitting a key. He refined the design to remove the need to push a separate button with every keypress, with two switches on every key: one to produce the control voltage determining pitch and the other to trigger the envelope generator. The envelope generator became a standard feature of synthesizers.<ref name=":2">{{Cite book |title=Analog Days: The Invention and Impact of the Moog Synthesizer |last1=Pinch |first1=Trevor |last2=Trocco |first2=Frank |publisher=[[Harvard University Press]] |year=2004 |isbn=978-0-674-01617-0 |pages=[https://archive.org/details/analogdaysinvent00trev/page/43 43] |url=https://archive.org/details/analogdaysinvent00trev/page/43}}</ref>
 
Following discussions with the engineer and composer [[Vladimir Ussachevsky]], (thenthe head of the [[Columbia-Princeton Electronic Music Center]]), in 1965, Moog developed a new envelope module whose functions were described in f T1 (attack time), T2 (initial decay time), ESUS (sustain level), and T3 (final decay time). These were later simplified to the modern ADSR form (Attackattack time, Decaydecay time, Sustainsustain level, Releaserelease time) by [[ARP Instruments, Inc.|ARP]].<ref name=":2" />
 
=== ADSR ===
[[File:ADSR parameter.svg|thumb|213px|Schematic of ADSR]]The most common kind of envelope generator has four stages: attack, decay, sustain, and release (ADSR).<ref name=":0">{{Cite book|url=https://books.google.com/books?id=EFepAgAAQBAJ&q=synthesizer|title=The Synthesizer: A Comprehensive Guide to Understanding, Programming, Playing, and Recording the Ultimate Electronic Music Instrument|last=Vail|first=Mark|publisher=OUP USA|year=2014|isbn=9780195394894|language=en}}</ref>
 
*'''Attack''' is the time taken for initialthe run-uprise of the level from nil to peak, beginning when the key is pressed.
*'''Decay''' is the time taken for the subsequentlevel runto downreduce from the attack level to the designated sustain level.
*'''Sustain''' is the level during the main sequence of the sound's duration,maintained until the key is released.
*'''Release''' is the time taken for the level to decay from the sustain level to zero after the key is releasednil.<ref>{{Cite web |url=https://www.musicradar.com/tuition/tech/how-to-use-basic-adsr-filter-envelope-parameters-578874 |title=How to use basic ADSR filter envelope parameters |website=MusicRadar |date=June 21, 2013 |language=EN-GB |access-date=2018-12-16}}</ref>
 
While attack, decay, and release refer to time, sustain refers to level.<ref name=":0" />
 
=== Other envelopes ===
{{More citations needed section|date=January 2020}}
Some electronic musical instruments can invert the ADSR envelope, reversing the behavior of the normal ADSR envelope. During the attack phase, the modulated sound parameter fades from the maximum [[amplitude]] to zero then, during the decay phase, rises to the value specified by the sustain parameter. After the key has been released the sound parameter rises from sustain amplitude back to maximum amplitude.
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Some envelopes, such as that of the [[Korg MS-20]], have an extra parameter, hold. This holds notes at the sustain level for a fixed length of time before decaying. The [[General InstrumentsInstrument AY-3-89128910]] [[sound chip]] includes only a hold time parameter; the sustain level is not programmable.
 
Another common variation in the same vein is the AHDSR (attack, hold, decay, sustain, release) envelope, in which the "''hold"'' parameter controls how long the envelope stays at full volume before entering the decay phase. Multiple attack, decay and release settings may be found on more sophisticated models.
 
Certain synthesizers also allow for a ''delay'' parameter before the ''attack''. Modern synthesizers, such as the [[Prophet '08]], have DADSR (delay, attack, decay, sustain, release) envelopes. The delay setting determines the length of silence between hitting a note and the attack. Some [[software synthesizers]], such as Image-Line's 3xOSC (included with their [[Digital audio workstation|DAW]] [[FL Studio]]) have DAHDSR (delay, attack, hold, decay, sustain, release) envelopes.
 
A common feature on many synthesizers is an AD envelope (attack and decay only). This can be used to control, e.g.for example, the pitch of one oscillator,<ref>{{cite book |title=Synthesizer technique |url=https://www.worldcat.org/title/synthesizer-technique/oclc/1036880013 |date=1987 |publisher=H. Leonard Books |page=64|oclc=1036880013 }}</ref> which in turn may be synchronized with another oscillator by [[oscillator sync]].
 
== See also ==
Retrieved from "https://en.wikipedia.org/wiki/Envelope_(music)"