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A functional music theory library for Javascript
TypeScript JavaScript HTML
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 - @tonaljs/key@3.4.1
 - @tonaljs/modules@3.4.2
 - @tonaljs/note@3.2.5
 - @tonaljs/scale@3.3.1
Latest commit 8b9f9eb Jan 8, 2020


npm version build status minified size gzipped size

tonal is a music theory library. Contains functions to manipulate tonal elements of music (note, intervals, chords, scales, modes, keys). It deals with abstractions (not actual music or sound).

tonal is implemented in Typescript and published as a collection of Javascript npm packages.

It uses a functional programing style: all functions are pure, there is no data mutation, and entities are represented by data structures instead of objects.


Install all modules:

npm install --save @tonaljs/modules

Or individually:

npm install --save @tonaljs/note @tonaljs/key


Tonal is compatible with both ES5 and ES6 modules, and browser.

ES6 import:

import { Tonal, Scale } from '@tonaljs/modules';
// or individually
import * as Tonal from "@tonaljs/tonal";

ES5 require:

const { Tonal, Scale } = require('@tonaljs/modules');


Grab the minified browser ready version from the repository and include in the html file:

<script src="tonal.min.js"></script>

Bundle size

@tonaljs/modules includes all published modules. Altough it is small (8kb gzipped), you can reduce bundle sizes by importing the modules individually, or even only the functions you need:

import { transpose } from '@tonaljs/tonal'
import { scale } from '@tonaljs/scale'


import { Tonal } from "@tonaljs/modules";
// or individually:
import * as Tonal from "@tonaljs/tonal";

Tonal.note("A4").midi; // => 60
Tonal.note("a4").freq; // => 440
Tonal.note("c#2").accidentals; // => '#'
Tonal.note("x").midi; // => undefined
Tonal.interval("5P").semitones; // => 7
Tonal.transpose("C4", "5P"); // => "G4"
Tonal.distance("C4", "G4"); // => "5P"


The API documentation lives inside file of each module:


Read contributing document for instructions


This library takes inspiration from other music theory libraries:


MIT License

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