MusicTheoryJS v2

Documentation | License(ISC)

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Music Theory Abstractions for analysis, synthesis, and real-time music composition. Designed for use with MIDI.

Includes nearly 70 pre-defined scale templates and over 40 pre-defined chords templates.

Designed to be an enterprise grade library that's easy to use and extend.

Examples:

import { Scale, Chord, Note, Instrument, buildTables } from "musictheoryjs";

// build the string tables
buildTables();

// create a note
const note = new Note("D4");

// create a scale
const scale = new Scale("C5(major)");
console.log(scale.getNoteNames()); // --> ["C5", "D5", "E5", "F5", "G5", "A5", "B5"]

// create a chord
const chord = new Chord("(Ab3)maj7");
console.log(chord.notes); // --> array of notes in the chord

// get the frequency of the scales 3rd degree
const instrument = new Instrument();
const freq = instrument.getFrequency(scale.degree(3)); // --> 659.26

// get the midi key for the scales 3rd degree
const midiKey = instrument.getMidiKey(scale.degree(3)); // --> 76

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A Note On Performance

The most performant and efficient way to create entities in MusicTheoryJS is to use Initializer objects e.g. {root: 5, octave: 3}. Using strings e.g. "C5(major)" is also fast when used the right way.

Each entity that accepts a string initializer uses an ideal format specified in the documentation. Using a format other what is prescribed will bypass the lookup table and the resulting performance will be much slower.

If you intend to use string initializers, you should probably use the buildTables function to create the lookup tables. Probably soon after the library loads.

import { buildTables } from "musictheoryjs";

buildTables();

This can be great for client side if you run buildTables in an async function and you present a spinner and/or prevent the user from creating new entities until the tables are built. This way you have control over the performance of your application.

Note: buildTables should only(optionally) be called once soon after your app loads and only if you intend to use string initialization.

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Installation

npm:

npm i musictheoryjs@latest

yarn:

yarn add musictheoryjs

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Usage

import * as mt from "musictheoryjs";
// or
import {
   Chord,
   Scale,
   Note,
   Instrument,
   Semitone,
   Modifier,
} from "musictheoryjs";

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Semitones

Semitones are simple numbers that represent notes
There are 12 in total ranging from 0(C) to 11(B)
0 -> C
1 -> C#
2 -> D
3 -> D#
4 -> E
5 -> F
6 -> F#
7 -> G
8 -> G#
9 -> A
10 -> A#
11 -> B

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Modifiers

Modifiers are this library's way of representing alterations.
Think of modifiers as the mathematical form.
Flat is represented as -1,
Sharp is represented as 1,
Natural is represented as 0.

You can import the Modifier enum or just create your own constants when needed.

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Instruments

Instruments encapsulate tuning and methods for calculating the frequency and midi key notes.

the tuning is specified as the A4 frequency in Hertz. The default tuning is 440Hz.

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Notes

Notes encapsulate the semitone and octave of a musical note.

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Chords

Chords are made from a root semitone, octave, template(containing ChordIntervals), and a base scale(default is the Major scale).

The following Pre-defined templates are available:

maj	maj4	maj6	maj69
maj7	maj9	maj11	maj13
maj7s11	majb5	min	min4
min6	min7	minAdd9	min69
min9	min11	min13	min7b5
dom7	dom9	dom11	dom13
dom7s5	dom7b5	dom7s9	dom7b9
dom9b5	dom9s5	dom7s11	dom7s5s9
dom7s5b9	dim	dim7	aug
sus2	sus4	fifth	b5
s11

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Scales

Scales are made from a key semitone, octave, template(a list of intervals).

The following Pre-defined templates are available:

major	minor	ionian	dorian
phrygian	lydian	mixolydian	aeolian
locrian	enigmaticMajor	enigmaticMinor	minor7b5
major7s4s5	harmonicMajor	harmonicMinor	doubleHarmonic
melodicMinorAscending	melodicMinorDescending	majorPentatonic	majorPentatonicBlues
minorPentatonic	minorPentatonicBlues	b5Pentatonic	minor6Pentatonic
dim8Tone	dom8Tone	neopolitanMajor	neopolitanMinor
hungarianMajor	hungarianMinor	hungarianGypsy	spanish
spanish8Tone	spanishGypsy	augmented	dominantSuspended
bebopMajor	bebopDominant	mystic	overtone
leadingTone	hirojoshi	japaneseA	japaneseB
oriental	arabian	persian	balinese
kumoi	pelog	algerian	chinese
mongolian	egyptian	hindu	romanian
hindu	insen	iwato	scottish
yo	istrian	ukranianDorian	petrushka
ahavaraba	halfDiminished	jewish	byzantine
acoustic

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Development

Step 1:
Fork the project

Step 2:
Create a new branch - Name it based on the work/feature your working on

Step 3:
From the project root(after you checkout your branch), run:

npm install

or

yarn install

Step 4:
Submit a pull request

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Scripts:

Build:

npm run build

or

yarn build

Test:

npm run test

or

yarn test

Lint:

npm run lint

or

yarn lint

Build Docs:

npm run build-docs

or

yarn build-docs