ADSR

ADSR stands for Attack, Decay, Sustain and Release, the four stages of an envelope generator that shapes how a sound changes from the moment a note starts until it fades to silence. Attack, decay and release are times; sustain is a level.

On a synthesizer or sampler, the ADSR envelope most often controls volume (the amp envelope) and filter cutoff (the filter envelope). It is the reason the same oscillator can become a pluck, a pad, a stab or a bass just by moving four controls.

What is an ADSR envelope?

An envelope generator does not make any sound of its own. It produces a control signal that rises and falls over time, and that signal moves another parameter with it: the level of an amplifier, the cutoff of a filter, the pitch of an oscillator. The envelope starts when the instrument receives a gate, which in practice is a key press or a MIDI note-on message. It keeps running while the key is held, and it moves into its final stage the moment the key is released.

In plain terms, the ADSR envelope is the blueprint of a note’s life: how quickly the sound fades in, how quickly the first burst settles, how loud it stays while you hold the key, and how long it takes to disappear after you let go.

The four stages

• Attack is the time it takes to rise from zero to the peak after the note starts. A short attack gives a hard, immediate start; a long attack makes the sound swell in.
• Decay is the time it takes to fall from that peak down to the sustain level, while the key is still held.
• Sustain is the level the envelope holds for as long as the key stays down. It is not a time. A sustain of 100% means there is effectively no decay; a sustain of 0% means the sound dies away even while you keep holding the note.
• Release is the time it takes to fall from wherever the envelope is to zero after the key is released.

If you let go of the key before the attack or decay has finished, most envelopes jump straight to the release stage from their current level. That is why a very short note played on a pad with a slow attack may barely be heard: it never reaches its full level.

How manufacturers and educators define it

Descriptions from the industry all point to the same idea. Native Instruments explains it as a tool for controlling how a sound changes over time, and Sweetwater stresses that changing the four stages alone can create a vast range of sounds.

One word, three kinds of envelope

The word envelope is used in three related but different ways in audio, and mixing them up causes a lot of confusion:

• Synthesis envelope: the user-defined ADSR contour inside a synth or sampler, triggered by notes. This is what this page is about.
• Dynamics envelope: the level-detection circuit inside a compressor, limiter or expander that follows the incoming signal and decides when to change gain.
• Temporal (amplitude) envelope: the natural rise and fall in level of any real sound, as studied in acoustics and psychoacoustics. Researchers separate this slow outline from the fast oscillations inside it, called the temporal fine structure (overview).

The history of ADSR

Before voltage-controlled synthesizers, electronic composers shaped notes by hand: riding faders, or cutting and splicing tape to create attacks and fades. Earlier instruments such as the Hammond Novachord (1939) already offered a few preset envelope shapes, but the adjustable, voltage-controlled envelope generator that became ADSR is tied to the birth of the Moog synthesizer.

A doorbell button and the first articulation

Composer Herbert Deutsch, who met Robert Moog in 1963 and worked with him on the first prototype, pointed out that the instrument needed a way to articulate notes rather than simply switching tones on and off. According to Deutsch’s own account, Moog sent him to a hardware store for a doorbell button to act as the trigger for an attack and decay (Herb Deutsch, Moog & Deutsch). It is a small detail, but it is the moment the envelope idea entered the synthesizer.

Moog described his voltage-controlled modules to the engineering world in the paper “Voltage-Controlled Electronic Music Modules”, presented at the Audio Engineering Society convention in New York in October 1964 and published in the Journal of the Audio Engineering Society in July 1965 (History of Information, original preprint).

Ussachevsky’s four parameters

The four-stage envelope as we know it came from a request by composer Vladimir Ussachevsky, head of the Columbia-Princeton Electronic Music Center. Following their discussions in 1965, Moog built an envelope module described by four parameters: T1 (attack time), T2 (initial decay time), ESUS (sustain level) and T3 (final decay time) (Envelope (music), citing Pinch and Trocco’s Analog Days).

How ARP gave us the name

The friendlier labels came from ARP Instruments. ARP’s envelope modules for the 2500 system used controls such as Attack, Initial Decay, Sustain and Final Decay (module documentation), and ARP later simplified the terms into the attack, decay, sustain, release shorthand that became universal. Today “ADSR” is used even for envelopes that have more or fewer stages.

From discrete circuits to chips

In the late 1970s, dedicated envelope chips made polyphonic synths practical, because every voice needed its own envelopes. The Prophet-5 used the SSM2050 envelope chip in its first two revisions and the Curtis CEM3310 from Rev 3 onwards (Synth DIY Wiki), while the SSM2056 was used in instruments such as the Korg Polysix.

Digital envelopes and beyond four stages

Digital synthesis broke the four-stage mould. The Yamaha DX7 (1983) gave each operator an envelope defined by four rates and four levels rather than a classic ADSR (Yamaha Black Boxes). In software synths, envelopes became graphical, with draggable curves, extra stages and looping. Xfer Serum (2014) made visible, bendable envelope curves the norm for a generation of producers, and Serum 2 followed in March 2025 (Bedroom Producers Blog). Matt Tytel’s free Vital (2020) and Native Instruments’ Massive X pushed further into multi-stage envelopes that can loop and double as LFOs.

How an ADSR envelope works

Gate and trigger

An envelope needs to know two things: when a note starts and when it ends. On most analogue systems this is a gate signal that goes high (typically +5 V or +10 V) when a key is pressed and falls to 0 V when it is released (early Moog systems used a switch-to-ground “S-trigger” instead). Some envelopes also accept a trigger, a short pulse that restarts the attack without holding the gate open. In software, MIDI note-on and note-off messages do the same job.

Analogue envelopes: charging a capacitor

Classic analogue envelope generators work by charging and discharging a capacitor through resistors whose values are set by the attack, decay and release controls. When the gate goes high, the capacitor charges through the attack resistor. A comparator detects when it reaches the peak and switches the circuit to discharge through the decay resistor, down to the voltage set by the sustain control, which is simply a voltage divider. When the gate goes low, the capacitor discharges to zero through the release resistor.

Because a capacitor charges and discharges along exponential curves, the stages of an analogue envelope are naturally curved: fast at first, then slowing down as they approach their target. That curve is a big part of why analogue envelopes are described as musical. Acoustic sounds also die away exponentially, so an exponential release sounds natural to the ear, while a straight-line fade often sounds abrupt at the end.

Digital envelopes: calculated sample by sample

In software and digital hardware, the envelope is calculated at audio or control rate. Many designs imitate the analogue behaviour with a simple recursive filter that approaches each target level exponentially, while others give the user direct control over the shape of each segment. The curve or tension controls in modern synths let you bend a stage from logarithmic through linear to exponential. Digital envelopes are also perfectly repeatable, with none of the drift that temperature can cause in old analogue circuits.

Amount, polarity, velocity and key tracking

• Envelope amount (depth) decides how far the envelope moves its destination. A filter envelope with zero amount does nothing, however you set the four stages.
• Inverted envelopes push the destination down instead of up, which is useful for pitch drops or filters that close on the attack.
• Velocity can scale the envelope amount or change its times, so harder notes open brighter or attack faster.
• Key tracking shortens or lengthens envelope times across the keyboard, mimicking acoustic instruments whose high notes decay faster than their low notes.
• Retrigger and legato modes decide whether a new note restarts the envelope from zero, restarts from its current level, or continues without retriggering when notes overlap, which matters a lot for monophonic basses and leads.

Types of envelopes

The four-stage ADSR is the reference, but many instruments use simpler or more elaborate shapes.

Envelope	Stages	Typical use
AR	Attack, Release	Simple instruments and modular systems; the sound sits at full level while the gate is held.
AD	Attack, Decay	Percussion. The envelope runs its course regardless of note length, as on drum machines where a single decay control sets the length of a kick or tom.
ADSR	Attack, Decay, Sustain, Release	The standard on most synths and samplers.
AHDSR	Adds Hold after the attack	Keeps the peak for a set time before decaying; useful for punchy basses and drums.
DADSR / DAHDSR	Adds a Delay before the attack	Lets one layer start later than another, for evolving pads and layered sound design.
Multi-stage (MSEG)	Any number of points	Drawn envelopes with custom curves; many can loop and behave like an LFO.

Some envelopes also loop between two stages while the key is held, which turns them into rhythmic modulation sources. At that point the line between an envelope and a low-frequency oscillator becomes blurry, and many modern synths deliberately merge the two.

ADSR in practice

Amp envelope versus filter envelope

The amp envelope shapes loudness; the filter envelope shapes brightness. Most classic synth sounds use both. One rule is worth remembering: the amp envelope is the master gate. If the filter envelope snaps open in 5 ms but the amp envelope takes two seconds to fade in, the filter movement happens while the sound is still almost silent, and you will never hear it.

Starting settings by sound

The numbers below are starting points for the amp envelope, not rules. Every synth scales its controls differently, so trust your ears over the display.

Sound	Attack	Decay	Sustain	Release
Pluck	0–5 ms	150–400 ms	0%	100–300 ms
Keys / chord stab	0–10 ms	200–600 ms	10–40%	150–300 ms
Lead	5–50 ms	200–400 ms	60–80%	100–250 ms
Pad	300 ms – 3 s	about 1 s	70–100%	1–4 s
Sub bass / 808-style	1–5 ms	set by note length	0–100%	20–150 ms

Plucks come from the filter

Most of the “pluck” character in a synth pluck comes from the filter envelope. Start with a bright waveform such as a sawtooth, set the cutoff low, give the filter envelope a positive amount, a fast attack, a short decay and zero sustain. Every note opens bright and closes quickly, which reads as a pluck even if the amp envelope is fairly long. This is the core of the classic trance and progressive house pluck.

Fit the release to the tempo

Release tails overlap in fast patterns. At 128 BPM a sixteenth note lasts about 117 ms, so a bassline with a 400 ms release smears every note into the next and builds up low-end mud. Set the release so the tail ends roughly where the next note begins, or switch the synth to mono/legato for basslines. In hip-hop and trap, producers often shorten the decay of an 808-style bass so it stops before the next kick, keeping the low end clean.

Avoid clicks in the first milliseconds

An attack of exactly 0 ms on a sine wave or sub bass can click if the waveform starts mid-cycle, and a release of 0 ms can click when the note is cut. One to five milliseconds of attack or release, or enabling oscillator phase reset, usually removes the click without softening the transient you actually hear.

Make it expressive with velocity

Routing velocity to the filter envelope amount, or to the attack time, makes harder notes brighter and punchier and softer notes rounder. It is one of the simplest ways to make a programmed part feel played rather than drawn in, and it is how acoustic instruments behave: a piano struck harder is brighter, not only louder.

Envelopes in samplers

Samplers apply the same idea to recorded audio, but the playback mode matters. In a one-shot mode the sample plays to the end once triggered, so the release control has little or no effect; Ableton’s Simpler, for example, replaces the ADSR with simple fade controls in its one-shot mode. In a classic or sustain mode the sample plays while the key is held and the release sets the fade after note-off, often with a loop keeping the sustain going.

Watch the release when you add reverb

A pad with a three-second release sent into a reverb with a four-second decay keeps feeding the reverb long after the key is up, and the result can be a wash that lasts far longer than the music needs. When you use long time-based effects, shorten the envelope release and let the effect provide the tail.

ADSR in your DAW

Every major DAW includes instruments built around ADSR envelopes, and several include tools that apply an envelope to any parameter.

DAW	Instruments with ADSR	Envelope tools for other parameters
Ableton Live	Operator, Wavetable, Drift, Simpler, Sampler	Envelope MIDI, a Max for Live modulator that applies an ADSR to up to eight mapped parameters (Live 12 manual)
Logic Pro	Alchemy, ES2, Retro Synth, Sampler	Modulator MIDI effect
FL Studio	Sytrus, FLEX, and the channel envelope on sampler channels	Fruity Envelope Controller
Cubase	Retrologue, Padshop	Modulators (Cubase Pro 14 and later), including an envelope follower
Fender Studio Pro (formerly Studio One)	Mai Tai, Impact XT	Built-in instrument envelopes
Pro Tools	Vacuum, Xpand!2	Instrument envelopes only
Bitwig Studio	Polysynth, Phase-4, Sampler	ADSR modulators that can be attached to any parameter
Reaper	ReaSynth, ReaSamplOmatic5000	Parameter modulation (LFO and audio follower rather than ADSR)

Two practical notes. First, if you want an envelope to shape recorded audio rather than a synth note, you need an envelope follower or a gate or transient tool, because a synth ADSR needs notes to trigger it. Second, Cubase’s EnvelopeShaper and similar transient designers are dynamics processors, not synth envelopes, despite the name.

Classic hardware and modern software

• Moog 911 Envelope Generator: the module from the Moog modular system that grew out of the Ussachevsky specification.
• ARP 2500 envelope modules (1003, 1033, 1046): the source of the attack, initial decay, sustain, final decay labels.
• Curtis CEM3310 and SSM2050/2056: the envelope chips that made affordable polysynths possible; CEM3310 clones are still used in modern modular gear.
• Roland TR-808: its drums use simple decay-style envelopes, and the bass drum’s decay control is the reason the 808 can be a short thump or a long boom.
• Yamaha DX7: four rates and four levels per operator, the template for many digital envelopes.
• Xfer Serum and Serum 2, Vital, Native Instruments Massive X: software synths whose graphical, curve-adjustable and multi-stage envelopes define how most producers work today.

What ADSR can’t do

ADSR is a model, and a simple one. It describes an idealised note with one rise, one fall and one plateau. Real instruments are more complicated, and knowing the limits helps you decide when to reach for extra envelopes or modulation.

Brass that gets brighter as it swells

In “Synthesizing Brass Instruments” (Sound On Sound, May 2001), part of his Synth Secrets series, Gordon Reid showed that in a brass note the lower harmonics reach their sustain level together and faster than the upper harmonics, so the tone brightens in a way a single amplitude envelope cannot capture. His solution was to drive a low-pass filter with its own ADSR, add velocity sensitivity to the filter envelope, and use pressure to vary brightness during the sustain.

The piano’s double decay

A piano note does not fade along a single curve. Most notes use two or three strings, and their coupled motion produces a fast initial decay followed by a much slower “aftersound”, an effect explained by physicist Gabriel Weinreich in the late 1970s (Weinreich, The coupled motion of piano strings). A single decay stage cannot reproduce it, which is why realistic piano instruments rely on sampling or physical modelling rather than one ADSR.

Common mistakes and myths

• Treating sustain as a time. Turning sustain up does not make the note longer; it makes the held part louder. If you want a longer tail after you let go, that is the release control.
• Confusing decay and release. Both make the sound fall, but decay happens while the key is held (from the peak down to the sustain level) and release happens only after the key is released.
• Leaving the default envelope on every patch. Init patches and many presets share similar envelopes, which is one reason a whole arrangement can sound flat and samey.
• Long releases on bass. Overlapping tails in the low end eat headroom and blur the relationship between kick and bass.
• Fixing in the mix what belongs in the envelope. Reaching for a compressor or transient shaper to tame a pad that swells in too slowly, instead of shortening the attack.
• Myth: an ADSR can model any acoustic instrument. It is an approximation. Many real instruments need several envelopes, velocity and pressure control, or sampling to sound convincing.

ADSR vs compressor attack and release

The same words appear on synths and on compressors, but they describe different things.

	Synth ADSR	Compressor attack and release
Triggered by	A note (gate or MIDI note-on)	The audio level crossing a threshold
What it does	Creates a shape and imposes it on the sound	Reacts to the incoming signal
Attack means	Time to rise to full level after the note starts	Time to apply gain reduction after the signal exceeds the threshold
Release means	Time to fade out after the note ends	Time to stop reducing gain after the signal falls back below the threshold
Sustain	A level held while the key is down	No equivalent

In short, a synth envelope writes a contour onto the sound, while a compressor responds to the contour that is already there.

Related terms

• Transient: the fast initial peak that the attack stage shapes.
• Timbre: the tone colour that envelopes help define as much as harmonics do.
• Compressor and Expander: dynamics processors with their own attack and release controls.
• Arpeggiator: short arpeggiated notes depend heavily on decay and release.
• MIDI: note-on and note-off messages are what start and release the envelope.
• 808: the bass drum whose length is set by a decay envelope.
• Linear Arithmetic Synthesis: the Roland D-50 approach that pairs sampled attacks with synthesized sustains.

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