keys.js 🎹

A helper library written in Javascript to help with the development of music-oriented web applications. It is very basic at the moment due to it only being used for a personal project that simply needs these common functions so far, but it can:

• Calculate a frequency based on the number of semitones away from A4 (assumed 440Hz tune)
• Calculate a frequency based on a MIDI note number (not piano note)

I hope in the future I can get it to:

• Take into account different tuning frequencies for its base calculation
• Calculate a frequency based on a musical note and octave i.e. F#4, D2
• Allow detuning by cents to alter frequency calculation bias
• Convert a musical note to semitone difference from root
• Convert a MIDI note to a musical note
• And any other conversions in between
• Be available as an ES Module

Install & usage

Install with either

npm i @liamjcooper/keys.js

or...

yarn add @liamjcooper/keys.js

And then to use, you can either

const { frequency } = require("@liamjcooper/keys.js");

or...

const frequency = require("@liamjcooper/keys.js/dist/frequency");

Documentation

Currently, you only have the choice of converting a semitone difference or MIDI note to a frequency as a float.

To do either conversion:

frequency.forSemitoneFromRoot(3) // 523.251... (3 notes up from A4)
frequency.forMidiNote(66) // 369.994... (3 notes down from A4)

Notes

All PRs welcome! Don't be afraid to say hi if this has helped you in any way, all feedback is also welcome 🙂