This sample program wraps https://github.com/schellingb/TinySoundFont (tinysoundfont) to play MIDI files via a LabSound AudioNode, and also https://github.com/rombankzero/pocketmod (pocketmod) to play MOD files via an AudioNode.
For reference on sound fonts, there's a great demo and archive of sound fonts here: https://github.com/surikov/webaudiofont (WebAudioFont)