Envelopes (ADSR)

An oscillator on its own just drones at one level forever. An envelope gives every note a shape: how fast it starts, how it settles, and how long it rings after you let go. Change the envelope and the same waveform becomes a pluck, a pad, an organ or a bass.

What is an Envelope?

An envelope is a shape that changes a setting over the life of one note. It starts when a key goes down (the note on) and finishes after the key comes up (the note off). Each new note restarts it.

The most common envelope has four stages, called ADSR:

Attack (a time): how long the sound takes to rise from silence to its peak after you press the key.
Decay (a time): how long it takes to fall from the peak down to the sustain level.
Sustain (a level, not a time): the level the sound holds for as long as you keep the key down.
Release (a time): how long it takes to fade to silence after you let go of the key.

Common mistake

Sustain is the odd one out. Attack, decay and release are measured in milliseconds or seconds. Sustain is measured as a level (0–100%, or in dB). A sustain of 0% does not mean "no sustain stage", it means the sound decays all the way to silence while you still hold the key.

The ADSR shape

level 100% | /\ | / \ S | / \_____________ | / \ 0% |/ \______ +--A--+-D-+------S------+--R--+→ time key down key up

The attack and decay happen right after the key goes down. The sound then sits at the sustain level until the key comes up, and the release starts from wherever the level is at that moment.

Hearing ADSR

The demo below starts on a pluck setting: a very fast attack, a short decay and a sustain of zero. Hold a key down. Notice that the sound fades away even though you are still holding it. That is what sustain 0% does.

Now compare a pad. The attack is slow (around 800 ms), the sustain is high and the release is long. Tap a key quickly and you'll barely hear it, because the attack never gets a chance to finish.

Note

A very short attack or release (under about 2 ms) on a sustained sound can cause a click. The waveform jumps instantly from silence to full level, and that sudden jump contains a burst of high frequencies. If you hear clicks at the start or end of notes, add 2–10 ms of attack or release.

Envelope Shapes for Common Sounds

Real instruments have recognizable envelopes. A piano note is loudest at the strike and then decays. A violin can swell in slowly. Copying these shapes is the quickest way to make a synth sound "like" something. Use this table as a starting point and adjust by ear.

Sound	Attack	Decay	Sustain	Release	Why it works
Pluck	0–5 ms	150–400 ms	0%	100–300 ms	Instant hit that dies away, like a plucked string
Pad	300 ms–2 s	500 ms–1 s	70–90%	1–3 s	Fades in and out smoothly, so chords blend into each other
Organ	1–5 ms	0–50 ms	100%	10–50 ms	Full level the whole time the key is held, stops almost instantly
Brass	30–100 ms	150–300 ms	60–80%	100–200 ms	A short swell into the note, like a player pushing air
Swell / reverse	1–3 s	0–100 ms	100%	500 ms–1 s	Builds slowly, great for transitions and ambient beds
Bass	0–5 ms	150–400 ms	50–80%	30–80 ms	Punchy start, steady body, short tail so notes don't smear together

Producer tip

Release time affects your mix, not just the sound. A long release on a bass makes each note overlap the next one, which muddies the low end. Keep bass releases short (under about 100 ms) and save long releases for pads and leads that sit higher up.

Amp, Filter & Pitch Envelopes

An envelope is just a control shape. You can point it at any setting. Most synths give you at least two envelopes, and many let you assign more.

Amp envelope

The amp envelope controls volume. It is the one you have been using above, and every synth has one. It decides whether a sound is short or long, soft or punchy.

Filter envelope

The filter envelope moves the filter cutoff during the note. The envelope amount (sometimes called depth or env mod) sets how far it moves. With a low cutoff, a fast attack and a short decay, the filter opens wide for a moment and then closes. You hear a bright "pew" or "bow" at the start of each note. This is the classic sound of the Roland TB-303 acid bass and of most synth plucks.

Some synths allow a negative amount. The cutoff then drops at note-on and rises back up, which gives a darker, "backwards" movement. See Filters for how cutoff and resonance work.

Pluck = amp envelope + filter envelope

Oscillator: Saw Filter cutoff: 400 Hz, resonance 25% Filter env: A 0 ms D 250 ms S 0% R 200 ms amount +60% Amp env: A 1 ms D 300 ms S 0% R 200 ms

The filter envelope makes each note bright at the start and dark at the end. The amp envelope makes the note fade. Together they sound much more like a real plucked string than either one alone.

Pitch envelope

The pitch envelope bends the pitch during the note. Short pitch envelopes are everywhere in electronic drums. A synthesized kick drum is usually a sine wave that starts high and drops quickly:

Kick drum pitch envelope

Oscillator: Sine Pitch: starts around 150–200 Hz drops to about 45–55 Hz in 30–120 ms Amp env: A 0 ms D 300–600 ms S 0% R 50 ms

The fast pitch drop is heard as the "click" or "punch" of the kick. The low tail is the body. A longer pitch drop sounds like a booming 808. A very short one sounds tight and clicky, like techno. You'll build this from scratch in Sound Design Recipes.

Other uses: a few semitones of pitch drop on a lead adds a "zap" to the start of each note, and a slow upward pitch envelope on noise makes a riser.

Envelope Curves: Linear vs Exponential

Each stage of an envelope follows a curve. Some synths let you bend it.

Linear: the level changes at a constant rate, like a straight ramp.
Exponential: the level changes fast at first, then slows down (or the other way round).

Our ears hear loudness on a roughly logarithmic scale. Because of that, a linear decay tends to sound like it hangs at full volume and then drops off suddenly at the end. An exponential decay sounds smooth and natural, because real sounds (a plucked string, a struck drum) fade this way. Analog synth envelopes are built from charging and discharging capacitors, so their curves are naturally exponential-shaped. That is part of why vintage envelopes are often described as "snappy".

Curve	Sounds like	Good for
Linear attack	Even, gradual fade-in	Pads, swells
Exponential decay	Fast drop, then a long gentle tail	Plucks, drums, pianos, snappy basses
Linear decay/release	Holds, then cuts off near the end	Gated effects, some 808 tails

Extra stages

Many synths add stages to the basic four. Hold (AHDSR) keeps the level at its peak for a set time before the decay starts, which helps drums and plucks punch. Delay (DAHDSR) waits a set time before the attack begins, which is handy for an envelope that only kicks in on long notes.

Velocity & Envelopes

Velocity is how hard you hit a key, sent as a number from 1 to 127 (see MIDI). Routing velocity to an envelope makes a synth feel alive, because soft and hard notes behave differently.

Velocity → amp level: harder notes are louder. This is the default on most synths.
Velocity → filter envelope amount: harder notes open the filter further and sound brighter. Real instruments work like this. A piano struck hard is brighter, not just louder.
Velocity → attack time: harder notes get a shorter attack, so they bite. Soft notes fade in.

Try it in your DAW

Load your DAW's stock synth on a new MIDI track [Ableton: Analog or Drift; FL Studio: 3x Osc or FLEX; Logic: Retro Synth or ES2] and pick an init or default patch.
Set oscillator 1 to a saw wave. Program a four-note chord, each note 1 bar long, at 120 BPM.
Make it a pad: amp attack about 800 ms, decay 500 ms, sustain 80%, release 1.5 s. Play it back.
Make it an organ: attack 2 ms, sustain 100%, release 20 ms. Notice how chord changes become abrupt.
Make it a pluck: attack 1 ms, decay 300 ms, sustain 0%, release 200 ms. Change the notes to 1/8 notes.
Now lower the filter cutoff to around 500 Hz and raise the filter envelope amount. Copy the amp envelope settings to the filter envelope and compare the pluck before and after.
Finally, map velocity to filter envelope amount (look in the synth's modulation or velocity section). Draw some notes at velocity 40 and some at 120 and listen.

Producer tip

Compressors and gates also have attack and release controls. The idea is the same: how fast the effect reacts and how fast it lets go. Once ADSR feels natural, Compression will be much easier to understand.

The four stages of a basic envelope are attack, , sustain and .

Sustain is measured as a , not a time.

A synthesized kick is usually a wave with a fast downward envelope.

Next, learn how to add movement that repeats over time in LFOs & Modulation.

1. You hold a key down, but the note fades to silence anyway. Which setting causes this?

A long attack
A long release
A sustain of 0%
A short attack

With sustain at 0%, the decay stage falls all the way to silence while the key is still held. That's the classic pluck shape.

2. Which envelope fits a soft, slow-moving pad best?

A 1 ms, D 100 ms, S 0%, R 50 ms
A 2 ms, D 0 ms, S 100%, R 20 ms
A 5 ms, D 300 ms, S 70%, R 50 ms
A 900 ms, D 600 ms, S 80%, R 2 s

Pads need a slow attack and long release so chords fade in and blend into each other.

3. What does a filter envelope with a fast decay and a low cutoff produce?

A bright "pew" at the start of each note that quickly darkens
A slow vibrato
A louder note
A stereo widening effect

The envelope opens the filter for a moment, then closes it. That bright-to-dark movement is the sound of plucks and acid basses.

4. Why do exponential decays usually sound more natural than linear ones?

They use less CPU
They are always longer
They add harmonics
Real sounds fade that way, and our ears hear loudness on a roughly logarithmic scale

A linear fade sounds like it hangs and then drops suddenly. An exponential fade matches how strings and drums actually die away.

5. You hear a click at the start of every note on a sustained synth. What is the simplest fix?

Raise the sustain
Lengthen the attack to a few milliseconds
Turn up the resonance
Shorten the release to 0 ms

An attack near 0 ms makes the waveform jump instantly, which clicks. 2–10 ms of attack smooths it out without making the sound feel slow.