Playing Sounds

Sonic Pi has two fundamental ways to make sound: samples (pre-recorded audio) and synths (mathematically generated sound). Understanding both is essential.

Samples

Samples are recordings. Sonic Pi includes hundreds built-in.

sample :bd_tek       # Techno kick drum
sample :sn_dub       # Dub snare
sample :drum_cymbal_closed  # Hi-hat
sample :bd_boom      # Boomy kick

Sample Parameters

Every sample can be modified:

sample :bd_tek,
  amp: 2,           # Volume (1 = default, 2 = twice as loud)
  rate: 0.9,        # Playback speed (0.5 = half speed, 2 = double)
  attack: 0,        # Fade in time
  release: 0.5,     # Fade out time
  cutoff: 100       # Low-pass filter frequency

amp (amplitude)

Controls volume. Values above 1 boost, below 1 reduce.

sample :bd_tek, amp: 0.5   # Quiet
sample :bd_tek, amp: 1     # Normal
sample :bd_tek, amp: 2.5   # Loud (used in our kicks)

rate

Changes playback speed AND pitch:

sample :bd_tek, rate: 0.5  # Half speed, octave lower
sample :bd_tek, rate: 1    # Normal
sample :bd_tek, rate: 2    # Double speed, octave higher
sample :bd_tek, rate: -1   # Reversed!

We often use rate: 0.9 on kicks to lower the pitch slightly for more weight.

cutoff

Low-pass filter — removes frequencies above this value:

sample :bd_tek, cutoff: 60   # Dark, muffled
sample :bd_tek, cutoff: 100  # Balanced
sample :bd_tek, cutoff: 130  # Bright, all frequencies

Finding Samples

Sonic Pi groups samples by type:

# Drums
sample :bd_tek, :bd_haus, :bd_boom, :bd_zum   # Kicks
sample :sn_dub, :sn_dolf, :sn_zome            # Snares
sample :drum_cymbal_closed, :drum_cymbal_open # Hi-hats

# Electronic
sample :elec_twang, :elec_blip, :elec_ping

# Ambient
sample :ambi_choir, :ambi_dark_woosh

In Sonic Pi, type sample : and press Ctrl+Space to see all options.

Synths

Synths generate sound mathematically. They’re more flexible than samples.

use_synth :prophet
play 60           # Play MIDI note 60 (middle C)

Or use note names:

play :c4          # Middle C
play :d2          # D, two octaves below middle C
play :fs4         # F sharp, fourth octave

Choosing a Synth

use_synth :prophet    # Warm, fat analog sound
play :c3

use_synth :tb303      # Acid bass, squelchy
play :c2

use_synth :dsaw       # Aggressive, wide
play :c3

use_synth :sine       # Pure tone, no harmonics
play :c2

We’ll explore synths deeply in Part II.

Synth Parameters

use_synth :prophet
play :c4,
  amp: 0.5,         # Volume
  attack: 0.1,      # Time to reach full volume
  decay: 0.2,       # Time to drop to sustain level
  sustain: 0.3,     # Hold time
  release: 0.4,     # Fade out time
  cutoff: 80        # Filter brightness

The attack, decay, sustain, release parameters form the ADSR envelope — more on this in Part II.

Playing Chords

Play multiple notes simultaneously:

play [:c4, :e4, :g4]           # C major chord
play chord(:c4, :minor)        # C minor chord
play chord(:d3, :m7)           # D minor 7th

Or play separately in quick succession:

play :c4
play :e4
play :g4

Without sleep, all three play at once.

Samples vs Synths: When to Use Which

Use samples for:

• Drums and percussion (more realistic)
• Sound effects
• When you need a specific “real” sound

Use synths for:

• Bass (precise pitch control)
• Leads and melodies (expressiveness)
• Pads and atmospheres (sustain control)

Layer both:

# Our kick: sample for punch, synth for sub
define :kick do |v=1|
  sample :bd_tek, amp: 2*v, rate: 0.9
  sample :bd_boom, amp: 0.5*v, rate: 1.2
end

Quick Reference

# Samples
sample :bd_tek, amp: 2, rate: 0.9, cutoff: 100

# Synths
use_synth :prophet
play :c4, amp: 0.5, attack: 0.1, release: 0.5, cutoff: 80

# Chords
play [:c4, :e4, :g4]
play chord(:c4, :minor)

Next: Timing and Sleep — how to control when sounds happen.