Harmonics

Harmonics is a small node module that contains utility functions for working with musical scales and chords. The library exposes lists of available scales and chords along with helpers to retrieve notes, parse inline chord notation and compute scale intervals. The scale and chord data is generated using tonal and additional sources such as the Melakarta ragas.

Project Structure

harmonics/
├── src/                # Library source files
│   ├── index.js        # Exports library functions
│   ├── scalesAndChords.js  # Core logic for chords & scales
│   └── scalesAndChords.test.js  # Jest tests
├── gen/                # Generated data and generator script
│   ├── chordMaps.json
│   ├── scaleMaps.json
│   ├── melakarta.json
│   ├── svara.json
│   └── index.js        # Script to generate JSON maps
├── package.json        # NPM configuration
├── babel.config.js
├── webpack.config.js
└── README.md

Install

npm install harmonics

Interface

Use harmonics in your project

const harmonics = require('harmonics');

Get an array of all the scales available in harmonics (includes the one's from Tonal and the Melakarta ragas).

harmonics.scales(); // ['ionian', 'dorian', 'lydian', '...', 'Kanakangi', 'Ratnangi', '...']

Get the notes of a scale as an array

harmonics.scale('C4 major'); // ['C4', 'D4', 'E4', 'F4', 'G4', 'A4', 'B4']

Scales available from Tonal are lower cased while ragas have their first letter capitalized.

harmonics.scale('C4 Kanakangi'); // ['C4', 'Db4', 'D4', 'F4', 'G4', 'Ab4', 'A4']

Get an array of all the available chords (with numeric chords such as 4, 5, 7 etc exposed as 4th, 5th, 7th)

harmonics.chords(); // ['M', 'm', 'maj7', '4th']

Get the notes of a chord as an array (defaults to the 4th octave)

harmonics.chord('C4 M'); // ['C4', 'E4', 'G4']

Get the notes of a chord as an array for a specific octave

harmonics.chord('C5 M'); // ['C5', 'E5', 'G5']

Get the notes of an "inline" chord such as CM or Cmaj7 or Dbsus4_6 (here 6 is the octave). This is used in Scribbletune where you can define a bunch of notes and use chords in between, e.g 'C4 E4 Csus2 G4' (here Csus2 is "inlined" with C4, E4 and G4)

harmonics.inlineChord('CM'); // ['C4', 'E4', 'G4']
harmonics.inlineChord('CM_5'); // ['C5', 'E5', 'G5']

Get the indices of a scale/raga or bitmap

harmonics.getIndicesFromScale('phrygian'); // [0, 1,  3,  5, 7, 8, 10, 12]
harmonics.getIndicesFromScale('110010110011'); // [0, 1,  3,  5, 7, 8, 10, 12]

Development

Install dependencies and run tests:

npm install
npm test

Build the browser bundle:

npm run build

For continuous browser builds during development:

npm run watch:browser

Run the tests in watch mode:

npm run test:watch

To regenerate the scale and chord data run:

node gen/index.js

Further Learning

• Explore the JSON maps under gen/ to understand how scales and chords are represented.
• Look at src/scalesAndChords.js for the core logic behind the exported functions.
• Modify gen/index.js if you wish to add or update scale and chord definitions.