sketch_quickmusic.js

This example demonstrates use of the quickMusic.js lib. This is a quick and dirty library with a few functions and properties that might help in quickly creating generative music.

Properties

• scales.major
• scales.minor
• scales.phrygianDominate
• scales.minorPentatonic

Functions

• getNoteInScale(position, tonic, scale)
• midiToName(number)
• nameToMIDI(name, octave)
• imposePhrase(phrase, tonic, scale)
• shiftPhrase(phrase, amount)
• clonePhrase(phrase)

For more the details, see the comments in quickMusic.js

setup() is called by p5 kick off the program.

function setup() {
	createCanvas(640, 360);
	var synth = new MonoSynth();
	synth.playNotes(makeSongQuickMusic());
}

makeSongQuickMusic() creates the song, using quickMusic to make things a bit easier

function makeSongQuickMusic() {
	var song = [];

Create an array of the pitches we’ll use in the song. Rather than using midi note numbers, this array holds positions on scale. Using scale positions is easier, because we won’t need to think about what notes to skip. It also lets us decide on the key later.

All positions in one octave of a diatonic (7-pitch) scale (e.g. major)

	var positions = [0, 1, 2, 3, 4, 5, 6];

Start at a random index.

	var index = floor(random(positions.length));

Let’s make 16 notes.

	for (var i = 0; i < 16; i++) {

Pick a step amount at random from a list, step that much.

		index = index + sample([-1, 0, 1]);

Make sure we don’t go outside the array bounds.

		index = constrain(index, 0, positions.length - 1);

Push the note onto the song.

		song.push([
			positions[index],
			sample([1 / 2, 1 / 4, 1 / 4, 1 / 4])
		]);
	}

At this point the song is an array that looks something like this:

[
[1, 1/2],
[0, 1/4],
...
]

The first number in each note represent a position in a scale, rather than the actual midi note number to play. We can use quickMusic.imposePhrase to convert those positions to their corresponding notes.

This will “impose” the phrase into C-minor.

	song = quickMusic.imposePhrase(song, quickMusic.nameToMIDI("C", 3), quickMusic.scales.minor);

Return our finished song.

	return song;
}

sample() recieves and array, selects an item in the array randomly, and returns it

function sample(a) {
	return a[floor(random(a.length))];
}