---
title: Tonal API
layout: ../../layouts/MainLayout.astro
---

import { MiniRepl } from '../../docs/MiniRepl';
import { JsDoc } from '../../docs/JsDoc';

# Tonal API

The Tonal API, uses [tonaljs](https://github.com/tonaljs/tonal) to provide helpers for musical operations.

### transpose(semitones)

Transposes all notes to the given number of semitones:

<MiniRepl client:only="react" tune={`"c2 c3".fast(2).transpose("<0 -2 5 3>".slow(2)).note()`} />

This method gets really exciting when we use it with a pattern as above.

Instead of numbers, scientific interval notation can be used as well:

<MiniRepl client:only="react" tune={`"c2 c3".fast(2).transpose("<1P -2M 4P 3m>".slow(2)).note()`} />

### scale(name)

Turns numbers into notes in the scale (zero indexed). Also sets scale for other scale operations, like scaleTranspose.

<MiniRepl
  client:idle
  tune={`"0 2 4 6 4 2"
.scale(seq('C2 major', 'C2 minor').slow(2))
.note()`}
/>

Note that the scale root is octaved here. You can also omit the octave, then index zero will default to octave 3.

All the available scale names can be found [here](https://github.com/tonaljs/tonal/blob/main/packages/scale-type/data.ts).

### scaleTranspose(steps)

Transposes notes inside the scale by the number of steps:

<MiniRepl
  client:idle
  tune={`"-8 [2,4,6]"
.scale('C4 bebop major')
.scaleTranspose("<0 -1 -2 -3 -4 -5 -6 -4>")
.note()`}
/>

### voicings(range?)

Turns chord symbols into voicings, using the smoothest voice leading possible:

<MiniRepl client:only="react" tune={`stack("<C^7 A7 Dm7 G7>".voicings('lefthand'), "<C3 A2 D3 G2>").note()`} />

### rootNotes(octave = 2)

Turns chord symbols into root notes of chords in given octave.

<MiniRepl client:only="react" tune={`"<C^7 A7b13 Dm7 G7>".rootNotes(3).note()`} />

Together with layer, struct and voicings, this can be used to create a basic backing track:

<MiniRepl
  client:idle
  tune={`"<C^7 A7b13 Dm7 G7>".layer(
  x => x.voicings('lefthand').struct("~ x").note(),
  x => x.rootNotes(2).note().s('sawtooth').cutoff(800)
)`}
/>

So far, we've stayed within the browser. [MIDI and OSC](/learn/input-output) are ways to break out of it.