etude.js

JavaScript Music Theory API

Try it here!

A port of etude, the Java version. While similar, there are a few changes to take note of:

• asList was removed due to the way arrays are implemented in JavaScript (JavaScript arrays can do most of what Java ArrayLists can do).

• Streams was ported for use with Letter and Scale. Contains filter, map, limit, and skip.

• Lack of most enum members. values, ordinal, and valueOf were ported (values was also "overloaded" via default parameters to take in startingElement where appropriate).

• Pitch not being Comparable. However, compareTo was ported.

• Complete alteration of utility methods. These were dependent on what was available in each respective language.

• Lack of type checks due to the differences between Java and JavaScript as languages. However, static type checks are available if using TypeScript.

• Any whole number will not contain a decimal point when converted to a string (e.g. 1.0 will be converted to "1.0" in Java whereas 1.0 will be converted to "1" in JavaScript). This is relevant for Value.DOUBLE_WHOLE and Value.WHOLE.

• Small syntactical changes

  Java	JavaScript	Reason
  EnumName.values().length	EnumName.size	To avoid cloning values array
  interval.getNumber()	interval.distance	number is a reserved word in JavaScript
  policy.test(key)	policy(key)	To allow let policy = k => {...} assignment

Installation

Browser

Add this line to your html file:

<script type="text/javascript" src="https://unpkg.com/etude/js/etude-browser.js"></script>

The src pulls from the latest version of etude on npm. This may cause builds to break if a backward-incompatible version is released. To target a specific version, include the version number in the src:

<script type="text/javascript" src="https://unpkg.com/etude@version/js/etude-browser.js"></script>

More information on the version tag can be found at unpkg.

If you do not wish to use unpkg, use Browserify along with the require methods below. If you do not wish to use either, download the file and add this line to your html file:

<script type="text/javascript" src="path/to/file/etude-browser.js"></script>

Any of the above methods adds etude to the global namespace. To avoid prepending module package names to each module name with each use (e.g. etude.theory.Letter), add these lines:

const {error, theory, util} = etude;
const {EtudeError} = error;
const {Accidental, Chord, Degree, Direction, Dynamic, Interval, Inversion, Key, KeySignature, Letter, Mode, MusicConstants, Note, Pitch, Policy, Scale, Tempo, TimeSignature, Value} = theory;
const {CircularIterator, CircularStream, ImmutablePrioritySet, InfiniteIterator, InfiniteStream} = util;

require

First install the package.

npm install etude

Then include the package in your code using one of the following methods:

Top level module:

const etude = require("etude");

This method requires you to prepend module package names to each module name with each use (e.g. etude.theory.Letter).

Each module separately:

const {error, theory, util} = require("etude");
const {EtudeError} = error;
const {Accidental, Chord, Degree, Direction, Dynamic, Interval, Inversion, Key, KeySignature, Letter, Mode, MusicConstants, Note, Pitch, Policy, Scale, Tempo, TimeSignature, Value} = theory;
const {CircularIterator, CircularStream, ImmutablePrioritySet, InfiniteIterator, InfiniteStream} = util;

Examples

For extensive example usage, refer to the Java version's unit tests.

Accidental

let accidental = Accidental.FLAT;
console.log(accidental.toString()); // b
console.log(accidental.getOffset()); // -1

accidental = Accidental.DOUBLE_SHARP;
console.log(accidental.toString()); // x
console.log(accidental.getOffset()); // 2

accidental = Accidental.fromOffset(-3);
console.log(accidental.toString()); // bbb
console.log(accidental === Accidental.TRIPLE_FLAT); // true

accidental = Accidental.fromString("n");
console.log(accidental.getOffset()); // 0
console.log(accidental === Accidental.NATURAL); // true

Chord

let chord = new Chord(Pitch.fromString("C4"), Chord.Quality.MAJOR);
console.log(chord.toString()); // [Cn4(48), En4(52), Gn4(55)]

chord = Chord
  .builder()
  .setRoot(Pitch.fromString("Ab4"))
  .add(Chord.Quality.MINOR)
  .add(Interval.fromString("M6"))
  .build();
console.log(chord.toString()); // [Ab4(56), Cb5(59), Eb5(63), Fn5(65)]

chord = Chord
  .builder()
  .setRoot(Pitch.fromString("C4"))
  .add(Chord.Quality.DIMINISHED_SEVENTH)
  .setInversion(Inversion.FIRST)
  .build();
console.log(chord.toString()); // [Eb4(51), Gb4(54), Bbb4(57), Cn5(60)]

Degree

let degree = Degree.TONIC;
console.log(degree.getValue()); // 1

degree = Degree.fromValue(5);
console.log(degree.toString()); // DOMINANT

Direction

let direction = Direction.ASCENDING;
console.log(direction === Direction.DEFAULT); // true

direction = Direction.DESCENDING;
console.log(direction !== Direction.DEFAULT); // true

Dynamic

let dynamic = Dynamic.PIANO;
console.log(dynamic.toString()); // p
console.log(dynamic.crescendo().toString()); // mp
console.log(dynamic.diminuendo().toString()); // pp

dynamic = Dynamic.fromString("mf");
console.log(dynamic === Dynamic.MEZZO_FORTE); // true
console.log(dynamic.crescendo() === Dynamic.FORTE); // true

Interval

let interval = new Interval(Interval.Quality.MAJOR, 6);
console.log(interval.getOffset()); // 9

interval = Interval.between(Pitch.fromString("Eb4"), Pitch.fromString("Ab4"));
console.log(interval.toString()); // P4

Inversion

let inversion = Inversion.ROOT;
console.log(inversion.getValue()); // 0

inversion = Inversion.THIRD;
console.log(inversion.getValue()); // 3 

Key

let key = new Key(Letter.C);
console.log(key.toString()); // C

key = new Key(Letter.G, Accidental.SHARP);
console.log(key.toString()); // G#

console.log(key.step(1).toString()); // A
console.log(key.step(2).toString()); // A#

key = new Key(Letter.F);
let ks = new KeySignature(Key.fromString("G"), KeySignature.Quality.MAJOR);
console.log(key.apply(ks).toString()); // F#

key = new Key(Letter.C, Accidental.FLAT);
console.log(key.sharp().toString()); // C#
console.log(key.none().toString()); // C
console.log(key.doubleFlat().toString()); // Cbb
console.log(key.isFlat()); // true

let anotherKey = key.getEnharmonicEquivalent(Letter.A);
console.log(anotherKey.toString()); // Ax
console.log(Key.isEnharmonic(key, anotherKey)); // true

key = Key.fromString("Eb");
console.log(key.getLetter() === Letter.E); // true
console.log(key.getAccidental() === Accidental.FLAT); // true

KeySignature

let ks = new KeySignature(Key.fromString("D"), KeySignature.Quality.MAJOR);

console.log(ks.keyOf(Degree.MEDIANT).toString()); // F#
console.log(ks.degreeOf(Key.fromString("G")).toString()); // SUBDOMINANT

console.log(ks.getKeysWithAccidentals().toString()); // F#,C#

let parallel = ks.getParallel();
console.log(parallel.getKey().toString()); // D
console.log(parallel.getQuality().toString()); // MINOR

let relative = ks.getRelative();
console.log(relative.getKey().toString()); // B
console.log(relative.getQuality().toString()); // MINOR

console.log(KeySignature.ORDER_OF_SHARPS.toString()); // F,C,G,D,A,E,B

Letter

let letter = Letter.A;
console.log(letter.getOffset()); // 9

letter = Letter.fromChar('c');
console.log(letter === Letter.C); // true

let letters = Letter
  .stream(Letter.E)
  .limit(10);
console.log(letters.toString()); // E,F,G,A,B,C,D,E,F,G

letters = Letter
  .stream(Direction.DESCENDING, Letter.C)
  .limit(8);
console.log(letters.toString());  // C,B,A,G,F,E,D,C

Mode

let mode = Mode.IONIAN;
console.log(mode.getStepPattern().toString()); // 2,2,1,2,2,2,1

MusicConstants

console.log(MusicConstants.KEYS_IN_OCTAVE); // 12
console.log(MusicConstants.SMALLEST_PROGRAM_NUMBER); // 0
console.log(MusicConstants.LARGEST_PROGRAM_NUMBER); // 127

Note

let note = new Note(Pitch.fromString("C4"), Value.QUARTER);
console.log(note.toString()); // C4(48)[QUARTER]

note = Note.fromString("Db5[1]");
console.log(note.getPitch().toString()); // Db5(61)
console.log(note.getValue().toString()); // WHOLE

Pitch

let pitch = new Pitch(Key.fromString("Bbb"), 4);
console.log(pitch.toString()); // Bbb4(57)

let ks = new KeySignature(Key.fromString("F"), KeySignature.Quality.MAJOR);
pitch = pitch.apply(ks);
console.log(pitch.toString()); // Bb4(58)

console.log(pitch.step(3).toString()); // C#5(61)
console.log(pitch.step(3, Policy.prioritize(Policy.FLAT)).toString()); // Db5(61)

let interval = new Interval(Interval.Quality.PERFECT, 4);
console.log(pitch.step(interval).toString()); // Eb5(63)

pitch = pitch.getHigherPitch(Key.fromString("C"));
console.log(pitch.toString()); // C5(60)

console.log(Pitch.isEnharmonic(Pitch.fromString("F#4"), Pitch.fromString("Gb4"))); // true

pitch = Pitch.fromProgramNumber(48);
console.log(pitch.toString()); // C4(48)

pitch = Pitch.fromString("Ax7");
console.log(pitch.getKey().equals(Key.fromString("Ax"))); // true
console.log(pitch.getOctave() === 7); // true

Policy

let policy = Policy.DOUBLE_FLAT;
console.log(policy(Key.fromString("C#"))); // false
console.log(policy(Key.fromString("Ebb"))); // true

policy = Policy.SHARPS;
console.log(policy(Key.fromString("C#"))); // true
console.log(policy(Key.fromString("C#x"))); // true

policy = Policy.matchLetter(Letter.E);
console.log(policy(Key.fromString("Dn"))); // false
console.log(policy(Key.fromString("Ebb"))); // true

let ks = new KeySignature(Key.fromString("A"), KeySignature.Quality.MAJOR);
policy = Policy.matchKeySignature(ks);
console.log(policy(Key.fromString("F"))); // false
console.log(policy(Key.fromString("F#"))); // true

let key = Key.fromString("G");
let policies = Policy.prioritize(Policy.TRIPLE_SHARP, Policy.TRIPLE_FLAT, Policy.NONE_OR_NATURAL);
console.log(key.step(2, policies).toString()); // Cbbb

Scale

let scale = new Scale(Key.fromString("Ab"), Scale.Quality.MAJOR);
let keys = scale
  .stream()
  .limit(8);
console.log(keys.toString()); // Ab,Bb,C,Db,Eb,F,G,Ab

keys = scale
  .stream(Direction.DESCENDING)
  .limit(8);
console.log(keys.toString()); // Ab,G,F,Eb,Db,C,Bb,Ab

scale = new Scale(Key.fromString("G"), Scale.Quality.HARMONIC_MINOR);
keys = scale
  .stream()
  .limit(8);
console.log(keys.toString()); // G,A,Bb,C,D,Eb,F#,G

keys = scale
  .stream(Policy.prioritize(Policy.TRIPLE_FLAT, Policy.DOUBLE_FLAT))
  .limit(8);
/**
 * NOTE: the first key is G despite the policy prioritizing TRIPLE_FLAT and DOUBLE_FLAT
 * this is because the scale was constructed with G being the initial key
 */
console.log(keys.toString()); // G,Cbbb,Cbb,Dbb,Fbbb,Fbb,Abbb,Abb

// apply the policy on the initial key
scale = new Scale(Key.fromString("G").getEnharmonicEquivalent(Policy.prioritize(Policy.TRIPLE_FLAT, Policy.DOUBLE_FLAT)), Scale.Quality.HARMONIC_MINOR);
keys = scale
  .stream(Policy.prioritize(Policy.TRIPLE_FLAT, Policy.DOUBLE_FLAT))
  .limit(8);
/**
 * NOTE: this begins with Abb
 */
console.log(keys.toString()); // Abb,Cbbb,Cbb,Dbb,Fbbb,Fbb,Abbb,Abb

Tempo

let tempo = Tempo.ANDANTE;
console.log(tempo.getBPM()); // 92
console.log(tempo.getBeatValue() === Value.QUARTER); // true
console.log(tempo.getTempoMarking()); // Andante

tempo = Tempo.PRESTO;
console.log(tempo.getBPM()); // 184
console.log(tempo.getBeatValue() === Value.QUARTER); // true
console.log(tempo.getTempoMarking()); // Presto

tempo = new Tempo(100, Value.HALF);
console.log(tempo.getBPM()); // 100
console.log(tempo.getBeatValue() === Value.HALF); // true
console.log(tempo.getTempoMarking()); // HALF = 100

tempo = new Tempo(150, Value.EIGHTH, "Pretty fast");
console.log(tempo.getBPM()); // 150
console.log(tempo.getBeatValue() === Value.EIGHTH); // true
console.log(tempo.getTempoMarking()); // Pretty fast

TimeSignature

let ts = TimeSignature.COMMON_TIME;
console.log(ts.getDurationOfMeasure()); // 1
console.log(ts.getBeatsPerMeasure()); // 4
console.log(ts.getOneBeat() === Value.QUARTER); // true

ts = new TimeSignature(6, 8);
console.log(ts.getDurationOfMeasure()); // 0.75
console.log(ts.getBeatsPerMeasure()); // 6
console.log(ts.getOneBeat() === Value.EIGHTH); // true

ts = new TimeSignature(3, Value.QUARTER);
console.log(ts.getDurationOfMeasure()); // 0.75
console.log(ts.getBeatsPerMeasure()); // 3
console.log(ts.getOneBeat() === Value.QUARTER); // true

Value

let value = Value.QUARTER;
console.log(value.toString()); // QUARTER
console.log(value.getDuration()); // 0.25

value = Value.fromString("0.25");
console.log(value === Value.QUARTER); // true

value = Value.fromString("QUARTER");
console.log(value === Value.QUARTER); // true

value = Value.fromString("1/4");
console.log(value === Value.QUARTER); // true

value = Value.fromDuration(0.25);
console.log(value === Value.QUARTER); // true