Wow! What a great tool. It's a really good source to get inspired. The UI is not very handy, but the random generator is. The final results might need some further polishing inside another tool, but I don't really care at the moment.
A procedural music generator that can generate MIDI files.
Created this back in 2013.
It originally had a server that could render WAV-files, but I later transformed it into client-only solution.
The source code for this generator is available here:
The following video shows an example of how it can sound if you use a proper MIDI synthesizer to render the result:
A more recent music generator is my WaveBots Editor