JavaScript ActionScript Ruby


jasmid - A Javascript MIDI file reader and synthesiser

Originally presented at BarCamp London 8, 13-14 November 2010

Open index.html in browser. Turn up volume. Click on link.

Sound output is via one of the following mechanisms, according to what your
browser supports:
* Mozilla Audio Data API <>
* Web Audio API
* a Flash fallback originally taken from dynamicaudio.js by Ben Firshman
    <> and hacked around by me.

The code:
stream.js - helper library for reading a string as a stream of typed data
midifile.js - parses the MIDI file format into a header and a list of tracks,
    each consisting of a list of event objects
replayer.js - steps over the data structure generated by midifile.js and calls
    the appropriate operations on the synthesiser
synth.js - audio synthesiser; generates waveforms according to tweakable
audio.js - passes the generated waveform to either the Audio Data API or the
    Flash fallback widget (da.swf)

* The only event types supported by replayer.js are note on, note off, tempo
    change and program change
* There are currently only two instrument presets defined in synth.js - one for
    strings and a 'piano' one for everything else - and neither of them are
    particularly good (just a single volume-modulated sine wave).

Matt Westcott <> - @gasmanic -