Understanding Amplitude Envelopes (ADSR)

The envelope is what gives a note its feel. It's the difference between a snap, a swell, a pluck, and a drone. Get this one under your belt and you've cracked one of the three foundations of every synth sound.

This is an interactive tutorial, and we want you to try out these techniques as we go. Use the ThinkSynth so you can hear how shaping the amp envelope changes the sound as we progress through this tutorial.

Watch the accompanying tutorial on our website.

Practice with ThinkSynth

What an envelope does

Without an envelope, a sound would just switch on and off like a light switch. The envelope is what shapes the sound over time: how quickly it starts, how it settles, how long it holds, how it fades. It's a huge part of why a piano (instant attack, slow decay) sounds nothing like a bowed violin (slow attack, full sustain), even when they're playing the same note.

The four stages

Attack (A): how long it takes to reach full level once you press a key.
Decay (D): how long it takes to fall from that peak down to the sustain level.
Sustain (S): the level the sound holds at for as long as the key is down.
Release (R): how long it takes to fade to silence once you let go of the key.

The point that trips everyone up: Sustain is a level, not a time.

Attack, Decay, and Release are all durations, measured in seconds (or milliseconds). Sustain is the odd one out: it's a volume, usually a value between 0 and 1 (or 0% to 100%). How long the sustain phase actually lasts is just how long you hold the key down. That's it.

Optional: envelopes can have more (or fewer) stages

ADSR is by far the most common shape, but it isn't the only one. Now and then you'll bump into:

AR (attackâ€“release): the simplest envelope going. You'll find it on basic drum modules and other percussion-focused gear. No decay, no sustain. The sound rises, then falls.
AD (attackâ€“decay): common for one-shot percussive sounds. The note plays its full shape no matter how long you hold the key down.
AHDSR: adds a hold stage between attack and decay. The envelope reaches the peak, sits there for a fixed amount of time, then starts to decay. Useful when you want a brief plateau before the body of the sound settles in.
Multi-stage envelopes (MSEGs): modern synths often let you draw whatever envelope shape you like, with as many stages as you want. Vital and Surge both have them, and we'll come back to them properly later on in the modulation module.

You don't need any of this to make great sounds. Plain old ADSR will get you 95% of the way there. But knowing these variants exist saves a lot of head-scratching the first time you open up a synth that hides "decay," or throws in an extra slider you weren't expecting.

Real-world analogies

Piano

Attack: instant. The hammer strikes the string straight away.
Decay: that loud impact settles fairly quickly down to a quieter ringing tone.
Sustain: the quieter ringing, held for as long as the key is down.
Release: let go of the key and the damper silences the string. Short release.

Bowed violin

Attack: slow. The bow takes a moment to grip the string and build volume.
Decay: minimal. The sound stays at full volume while you keep bowing.
Sustain: full level, held for as long as you keep bowing.
Release: lift the bow and the sound fades.

Two instruments everyone knows, two completely different envelopes. Same idea behind both, totally different feel.

Try it yourself

The widget below is a simple synth voice (a sawtooth wave) with an ADSR envelope shaping its volume. Have a play with the sliders, hit Play note, and watch the envelope curve update as you go. The preset buttons load the classic shapes from the Common shapes to try table below: pick one to load its settings, then hit Play note or Hold to hear it.

Common shapes to try

Sound	Attack	Decay	Sustain	Release	Character
Pluck	Short	Short	0	Short	A quick tap, there and gone. Like a pizzicato or a muted guitar pluck.
String swell	Long	Long	High	Long	Gradually builds and lingers. That section-of-strings feel.
Piano	Short	Long	Lowâ€“Mid	Short	Hammer hit, then a slow ringing decay.
Organ	Instant	0	Full	Very short	On/off like a switch. Steady tone the whole way through.
Brass	Defined	Moderate	Medium	Moderate	A bit of a sforzando. Punches in, then settles.

Your task

Open the ADSR playground above (or any synth you have to hand), and pick one sound from the Common shapes to try table.
Set the four controls - attack, decay, sustain and release - to match its description. Keep the same waveform throughout, so the only thing you're changing is the envelope.
Hit Play note (or Hold) and listen. Pay attention to how much the amp envelope alone changes the feel of the sound.
Select the matching preset to see our take on this sound.
Repeat for all five shapes. Recreating them from scratch, rather than just hitting the presets, is the best way to get ADSR amp envelopes under your fingers.

Learn more in

How To Use Synths

This worksheet is one small slice of our full synth course. If envelopes just clicked for you, there's plenty more where that came from, taught the same hands-on way.

Includes ThinkSynth PRO - the same synth as a VST/AU plugin you can drop straight into your DAW, so what you learn comes with you into your own tracks.

What you'll learn:

Waveforms, filters and amp envelopes from the ground up
Multiple oscillators, oscillator sync, sub-bass and noise
Poly, mono and legato modes, LFOs, the modulation matrix and MIDI Learn
Internal and external effects, plus wavetable, granular, FM and additive synthesis
How to pull presets apart and build your own from scratch

You also get:

Downloadable patches for Surge XT and Vital, so you can take apart the exact sounds your tutors make on screen.
Hands-on tasks at every step, including our MinusONE tracks where you drop in your own patches and finish a real piece of music.

Start now, finish anytime

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