Build a synth sound · Volta reference

A synthesizer creates sound from changing signals. You do not need a circuit diagram to begin: choose a starting tone, shape how bright it is, and decide how it begins and ends. Those three choices already cover a remarkable range of basses, leads, keys and pads.

Start with Your first sound if the code is new to you. Each example below is independent; replace the previous program with the whole next example when comparing them.

1. Choose the raw material#

An oscillator repeats a waveform. Its repetition rate determines pitch; its shape determines its mixture of overtones, which affects tone color or timbre.

Starting sound	What to listen for	Useful direction
`"sine"`	A smooth, pure tone	Sub bass, soft tones, FM building blocks
`"triangle"`	A soft tone with a little edge	Rounded basses, gentle leads
`"saw"`	A bright buzz	Filtered bass, strings, bold leads
`"square"`	A hollow, woody buzz	Retro leads, pulse-like basses

Listen for: the clean, rounded outline of the melody.

Listen to this example · four bars, then the tail

tempo = 120bpm
timingVersion = 2
play "sine" "c4 [e4 g4] b4 g4" |> release 120ms

Make it yours: replace "sine" with "saw". Keep the notes unchanged so you can concentrate on the tone. Then try "triangle" and "square".

2. Sculpt the brightness#

A low-pass filter lets low frequencies through and reduces higher ones. Its cutoff sets where that reduction begins. Raising the cutoff usually makes a harmonically rich sound brighter. Resonance emphasizes frequencies near the cutoff, giving a sweep a more pronounced vowel-like edge.

Listen for: the same saw-wave phrase becoming darker and brighter on alternate bars. The angle brackets choose one cutoff value per cycle.

Listen to this example · four bars, then the tail

tempo = 120bpm
timingVersion = 2
play "saw" "c3 eb3 g3 bb3"
  |> cutoff "<500 2400>"Hz
  |> resonance 2
  |> release 100ms

Make it yours: try "<300 4500>"Hz for a larger contrast. A filter cannot reveal high overtones that a pure sine did not contain; use the saw for this comparison. Explore the different colors in Filters.

3. Shape the beginning and ending#

An envelope changes a value over the life of a note. The common ADSR shape has four stages:

Stage	What it controls	A useful first experiment
Attack	Time to rise to full level	`5ms` for a quick start; `400ms` for a swell
Decay	Time to fall to the sustained level	Short for a pluck; longer for a soft key
Sustain	Level while the note is held	`0.2` is quiet; `0.8` stays strong
Release	Time to fade after the note ends	Short for separation; long for overlapping tails

Sustain is a level, not a duration. A note must last long enough for a slow attack to become audible.

Listen for: the notes swelling in and gently overlapping.

Listen to this example · four bars, then the tail

tempo = 120bpm
timingVersion = 2
play "saw" "c4 g4"
  |> cutoff 1800Hz
  |> attack 350ms
  |> decay 300ms
  |> sustain 0.55
  |> release 700ms
  |> reverb 0.37 0.18

Make it yours: change attack to 5ms and release to 80ms. The same oscillator now has a much more immediate, separated feel.

4. Build your own instrument#

A patch puts those choices in one reusable instrument. Inside a patch, pitch is the incoming note, freq pitch converts it to a frequency, and vel is the strength of the incoming hit. Multiplying gain by vel makes the patch respond to accents.

Listen for: a bright initial pluck that quickly becomes softer and darker.

Listen to this example · four bars, then the tail

tempo = 120bpm
timingVersion = 2
softpluck = patch {
  source = saw (freq pitch),
  ampEnv = adsr 5ms 180ms 0.15 160ms,
  filtEnv = adsr 2ms 220ms 0 100ms,
  cutoff = 500Hz + filtEnv * 2600Hz,
  resonance = 1.5,
  gain = vel * 0.3
}
play softpluck "c4 [eb4 g4] bb4 g4"

Make it yours: change the filter envelope's 220ms to 600ms. Listen for the brightness lingering after the initial hit. The amplitude and filter envelopes have separate jobs, even when they start together.

Choose your next kind of synthesis#

Technique	How it makes a sound	Explore
Subtractive	Start bright and remove frequencies	Filters, Analog character
FM and phase modulation	One oscillator changes another at audio speed	FM, phase and ring modulation
Wavetable	Move through a collection of waveforms	Wavetable synthesis
Additive	Combine individual partials	Additive synthesis
Physical modeling	Excite a model of a vibrating object	Strings and resonators
Granular	Layer tiny windows of recorded sound	Granular synthesis

Next: Bring a sound to life adds repeating movement, and The sound recipe book turns these ideas into instruments.