The ADSR Envelope

Every sound has a shape over time. The ADSR envelope controls that shape.

What is ADSR?

ADSR stands for:

• Attack — How quickly the sound reaches full volume
• Decay — How quickly it drops to the sustain level
• Sustain — The level held while the note plays
• Release — How quickly it fades after the note ends

Volume
  │    ┌──────┐
  │   /│      │\
  │  / │      │ \
  │ /  │      │  \
  │/   │      │   \
  └────┴──────┴────────► Time
   A    D   S    R

In Sonic Pi

use_synth :prophet
play :c4,
  attack: 0.1,    # 0.1 beats to reach full volume
  decay: 0.2,     # 0.2 beats to drop to sustain
  sustain: 0.5,   # Hold for 0.5 beats
  release: 0.3    # 0.3 beats to fade out

Total note duration = attack + decay + sustain + release = 1.1 beats

ADSR for Different Sounds

Punchy Bass (short, percussive)

attack: 0.01,   # Instant attack
decay: 0.2,     # Quick drop
sustain: 0.1,   # Short sustain
release: 0.15   # Quick release

Character: Tight, rhythmic, punchy

Pad (slow, evolving)

attack: 1.5,    # Slow fade in
decay: 0.5,     # Gentle drop
sustain: 2.0,   # Long sustain
release: 2.0    # Long fade out

Character: Atmospheric, washy, ambient

Lead (expressive)

attack: 0.05,   # Quick but not instant
decay: 0.25,    # Moderate drop
sustain: 0.4,   # Medium sustain
release: 0.5    # Smooth fade

Character: Musical, expressive, singable

Stab (aggressive hit)

attack: 0,      # Instant
decay: 0.1,     # Very quick
sustain: 0.05,  # Almost none
release: 0.1    # Quick fade

Character: Aggressive, punchy, rhythmic

Relative vs Absolute Duration

You can make ADSR relative to a note duration parameter:

define :lead do |n, dur=0.5, v=1|
  use_synth :prophet
  play n,
    amp: v,
    attack: dur * 0.1,     # 10% of duration
    decay: dur * 0.25,     # 25% of duration
    sustain: dur * 0.4,    # 40% of duration
    release: dur * 0.5     # 50% of duration (overlaps next note slightly)
end

lead :c4, 0.5   # Short note
lead :c4, 2.0   # Long note (same proportions)

This keeps the same “feel” regardless of note length.

Attack Shapes

Zero Attack (instant)

attack: 0

• Used for: Drums, stabs, bass
• Creates: Punchy, percussive sounds

Short Attack (0.01-0.05)

attack: 0.03

• Used for: Most bass, leads
• Creates: Quick but slightly softer entry

Medium Attack (0.05-0.2)

attack: 0.1

• Used for: Expressive leads, pads
• Creates: More musical, less aggressive

Long Attack (0.5+)

attack: 1.5

• Used for: Pads, atmospheric sounds
• Creates: Swelling, evolving textures

Release and Legato

Release affects how notes connect:

Short Release (staccato)

play :c4, release: 0.1
sleep 1
play :d4, release: 0.1

Notes are clearly separated.

Long Release (legato)

play :c4, release: 0.8
sleep 0.5
play :d4, release: 0.8

Notes overlap, creating smoother transitions.

ADSR in the Album

Kick Drum Pattern

Kicks don’t use ADSR directly (samples), but the concept applies:

• Instant attack (the transient)
• Quick decay (the punch)
• Minimal sustain
• Short release (tight low end)

TB303 Bass

use_synth :tb303
play :d2,
  attack: 0.01,
  decay: 0.2,
  sustain: 0.1,
  release: 0.15

Quick attack for punch, short overall for rhythmic bass lines.

Prophet Lead

use_synth :prophet
play :d4,
  attack: 0.05,
  decay: 0.25,
  sustain: 0.4,
  release: 0.5

Slightly softer attack for musical feel, longer release for expression.

Dark Ambience Pad

use_synth :dark_ambience
play :d3,
  attack: 1.5,
  sustain: 2.5,
  release: 3

Slow everything for atmospheric, evolving texture.

Quick Reference

Tips

1. Start with presets — Use the values above as starting points
2. Match the rhythm — Faster BPM often needs shorter ADSR
3. Leave space — Not everything needs long sustain
4. Release > Sleep — Notes can ring past the next sleep for legato
5. Attack affects feel — Even 0.01 vs 0.05 changes the vibe significantly