Svelte Piano

A typescript / svelte rewrite of the awesome AudioKeys project.

From the original project:

Use AudioKeys to power the QWERTY keyboard in your next Web Audio project. AudioKeys provides intelligent handling of key events, giving you key up and key down events that you can use to trigger your sounds.

AudioKeys provides configurable polyphony— if you're making a monophonic synth, choose from the common note priorities "last note", "first note", "highest note", or "lowest note". It also handles odd situations like switching tabs— AudioKeys fires a note off event when your browser window goes out of focus.

Installation

Using pnpm

pnpm install -D svelte-piano

Usage

<script>
	import { Piano } from 'svelte-piano';
</script>

<Piano />

Options

polyphony	The number of keys that can be active simultaneously.
notes	Whether or not to display the note names. Default false.
sound	Whether to load and play the stock keyboard sound.
width	Piano width in pixels.
height	Piano height in pixels.
theme	todo

<Piano
	options={
		polyphony: 1,
		notes: false,
		keys: true,
		sound: true
	}
	'--width': 900px;
	'--height': 250px;
 />

Note events

You can subscribe to note events using the onKeyDown, onKeyUp, and activeKeys stores.

<script>
	import { SveltePiano, onKeyDown, onKeyUp, activeKeys } from 'svelte-piano';

	$: console.log($activeKeys)

	$: $onKeyDown, () => {
		console.log($onKeyDown)
	}

	$: $onKeyUp, () => {
		console.log($onKeyUp)
	}
</script>

<Piano />

The Note interface:

interface Note {
	/**
	 * The keyCode of the key being pressed down.
	 */
	keyCode: number

	/**
	 * The midi number of the note.
	 */
	note: number

	/**
	 * The frequency of the note between 0 and 20,000.
	 */
	frequency: number

	/**
	 * On note down, the current velocity.
	 * On note up, 0.
	 */
	velocity: number

	/**
	 * Whether the key is currently being pressed down.
	 */
	isActive: boolean
}

These properties will be useful in setting up instruments. See the lib/Instrument.ts file for a simple example.

Headless API

If you're not using Svelte, you can use the keyboard directly. Options can be passed into the QwertyKeyboard constructor in an object or set individually using set.

// Headless vanilla keyboard.
const keyboard = new QwertyKeyboard({
  polyphony: 1,
  rows: 2,
  priority: 'lowest'
});

// Properties can also be set later.
keyboard.priority = 'highest'

Property	Description
polyphony	The number of keys that can be active simultaneously.
rows	Either 1 or 2.
octaveControls	Determines whether or not the z and x keys shift octaves when rows is set to 1.
velocityControls	Determines whether or not the number keys set the velocity of the notes being triggered.
priority	Determines the priority of the note triggers.
	"last": prefer the last note(s) pressed. "first": prefer the first note(s) pressed. "highest": prefer the highest note(s) pressed. "lowest": prefer the lowest note(s) pressed.
rootNote	Determines what note the lowest key on the keyboard will represent. The default is 60 (C4).

The default rootNote is 60 (C4). Keep in mind that setting it to a note other than C (36, 48, 60, 72, 84, etc.) will result in the key mappings not lining up like a regular keyboard!

For more on note priority, check out this Sound on Sound article.