This demo uses MIDI.js as a framework that bring MIDI to the browser. The midi data is generated by some fairly complex algorithms. The page will proceed to the next song automatically, or you can click here to generate a new song.
This may sound a bit simplistic. If you download the generated MIDI files yourself and render them using some more serious
music gear, you can get a far more impressive result. Go to this page and click "Random Midi4"
you can get actual .mid files.