This application is a analog synthesizer simulation built on the Web Audio API. It is very loosely based on the architecture of a Moog Prodigy synthesizer, although this is a polyphonic synthesizer, and it lacks the oscillator sync and glide effects of the Prodigy. (AKA: this is not intended to be a replication of the Prodigy, so pleased don't tell me how crappy a reproduction it is! :)
This uses my Web MIDI Polyfill to add MIDI support via the Web MIDI API - in fact, I partly wrote this as a test case for the polyfill and the MIDI API itself, so if you have a MIDI keyboard attached, check it out. The polyfill uses Java to access the MIDI device, so if you're wondering why Java is loading, that's why. It may take a few seconds for MIDI to become active - the library takes a while to load - but when the ring turns gray (instead of blue), it's ready. If you have a native implementation of the Web MIDI API in your browser, the polyfill shouldn't load - at the time of this writing, Chrome Stable (from version 43) has the only such implementation. Earlier versions of Chrome (from version 33) can enable Web MIDI via chrome://flags/#enable-web-midi
You can try it out live at https://webaudiodemos.appspot.com/midi-synth/index.html.
Check it out, feel free to fork, submit pull requests, etc.