Envelopes (ADSR)
A waveform tells you what the sound is. An envelope tells you how the sound behaves over time. When you press a key, does the sound slam in instantly like a drum hit, or does it swell in slowly like a string section? That's the envelope - the cooking technique that shapes every sound. Flash-fried or slow-simmered, same ingredient, different result.
The Four Stages
ADSR stands for Attack, Decay, Sustain, and Release. Together they describe the complete life of a sound from the moment you press a key to after you let go - from the first sizzle to the final plating.
Attack
How quickly the sound reaches full volume after you press the key. Short attack = instant hit (drums, plucks). Long attack = slow swell (pads, strings). Attack is the difference between a punch and a gentle push.
Decay
How quickly the sound drops from its peak to the sustain level. Short decay = percussive, sounds die quickly. Long decay = more gradual, natural fade after the initial hit.
Sustain
The volume level held while the key is pressed (after attack and decay). This is the only stage that's a level, not a time. Full sustain = organ-like (sound stays at full volume). Zero sustain = pluck-like (sound dies away even while holding the key).
Release
How quickly the sound fades after you let go of the key. Short release = sound stops immediately (staccato). Long release = sound lingers and trails off (reverb-like tail).
ADSR Recipes
Different combinations create completely different instruments:
Piano
Immediate attack with a natural decay that sustains while held.
Pad / Strings
Fades in gently, holds at a consistent level, trails off smoothly.
Pluck / Stab
Instant hit that dies away quickly regardless of whether you hold the key.
Organ
Full volume while held, silent the instant you release. On/off like a switch.
Envelopes Beyond Volume
ADSR doesn't just control volume - in most synths, you can assign envelopes to control anything. The most common use is controlling a filter's cutoff frequency over time.
Filter Envelope
Controls how the filter opens and closes over time. A fast attack and medium decay on a low-pass filter creates the classic "wah" at the start of each note - bright attack that mellows quickly.
Pitch Envelope
Controls pitch over time. A very short pitch sweep at the start of a note creates a "zap" or "laser" effect. Subtle pitch envelopes add a natural feel to synth sounds.
Production Tip
If a synth sound feels lifeless, try adjusting the attack and release first. Even tiny changes - adding 20ms of attack to soften the start, or extending the release slightly so notes overlap - can make a mechanical sound feel organic. The ADSR is often more important than which waveform you choose.
Try it
Keep the harmony the same and change only the envelope shape.
Same harmony - envelope shape changes the character entirely.
Key takeaway
ADSR envelopes shape how a parameter changes over a note's lifetime. Attack and release control the edges, decay and sustain control the middle. They turn static tones into expressive, dynamic sounds.
Next: adding cyclical movement and animation to sounds - LFOs.
Hear envelope shapes in action
Starts generates notes with different velocities and lengths, showing how envelopes shape each one.