###Setup Please make sure you have your environment configured to be able to install native node.js packages (required for audio support).

Run npm install nodesynth from the directory you'll be working in to download and install this package and all dependencies.

Then you can start node and play!

Usage

Require nodesynth in your JavaScript file like so: require('nodesynth')

From here, you only need to initialise a Synth object, set it's source property and call play

A small example:

var NodeSynth = require('nodesynth');

var ns = new NodeSynth.Synth({bitDepth: 16, sampleRate: 44100});
ns.play();

ns.source = new NodeSynth.Oscillator('sin', function(t){return 440 + ((t * 50) % 220)});

The library is built to be chainable, so you can pass an Oscillator as the frequency argument to the Oscillator constructor for example.

Oscillator

The Oscillator class takes two arguments to it's constructor, a function and the frequency

Valid values for function are:

• 'sin' or 'sine' for a sine wave
• 'cos' or 'cosine' for a cosine wave
• 'sq' or 'square' for a square wave
• 'tri' or 'triangle' for a triangle wave
• 'saw' or 'sawtooth' for a sawtooth wave
• Any function that accepts a phase parameter
• Any library object that has a valueAt(time) function

Note that phase is a value between 0 and 1 depending on the position of the current oscillation cycle. It will go from 0 to 1 at a rate of frequency times per second.

Note

There is an optional Note class that when required will pollute the global namespace with some useful variables such as A4, C3 - instances of a Note with their valueAt(time) parameter

Example:

var NodeSynth = require('nodesynth');
require('nodesynth/notes'); // Optional

var ns = new NodeSynth.Synth();
ns.play();

ns.source = new NodeSynth.Oscillator('sq', A4.perfect_unison());

Combining

All built-in library objects (Oscillator, Combiner) inherit functions from the Common class, which has methods such as mix, add.

add, subtract, divide, multiply, exponent and modulo all explain their mathematical function.

mix uses an algorithm to smoothly interleave the left and right hand sides to ensure they don't overflow the -1 and +1 boundaries of the audio signal.

An example (interesting alarm sound):

var NodeSynth = require('nodesynth');

require('nodesynth/notes');

var ns = new NodeSynth.Synth();
ns.play();

var o1 = new NodeSynth.Oscillator('sin', A4);
var o2 = new NodeSynth.Oscillator('sin', B5).multiply(new NodeSynth.Oscillator('sq', 1).add(1).multiply(0.5));

ns.source = o1.mix(o2);

This example creates a LFO square wave (1Hz), adds 1 to the amplitude (the wave is between -1 and +1, adding 1 moves it to 0-2 range) and then multiplies that by 0.5 (normalising it to between 0 and 1).

This LFO square wave is then multiplied by a sinewave oscillator at frequency B5, the result of which is that the square wave will cancel out the B5 sine wave when in the low position (B5 * 0 = 0), and play the sine wave normally when in the high position (B5 * 1 = B5). The combination of these functions is stored in variable o2.

o1 and o2 are then mixed and output to the speaker.

Try changing the oscillator functions and see how that affects the audio output.

Todo

• ~~Add a simple Note abstraction for doing stuff like new NodeSynth.Oscillator('square', C4)~~
• Add an Instrument abstraction with ADSR envelope
• Add a Sequence abstraction for describing a sequence of notes, times, strengths, etc.
• Add a Scale class with utility methods (first, second, tonic, subtonic, phygrian, )
• Add a Sampler for reading waveforms, performing FFT to get the frequency and rebuilding waveforms with the IFFT to modulate them
• ~~Add mixing functions such as add, subtract, multiply, mix, etc. (and mix them in...)~~
• Work out why there is so much latency (buffer size is small and so is samplesPerFrame...)
• Investigate using MIDI inputs to control parameters
• Lots more...

Nastiness

This library adds a valueAt(time) function to the Function and Number prototype's. May do away with this in future, but it definitely simplifies some backend stuff.