Music Mouse is an algorithmic musical composition software developed by Laurie Spiegel. It’s ported to web browsers by Tero Parviainen.
Spiegel’s best known and most widely used software, “Music Mouse – An Intelligent Instrument” (1986) is for Macintosh, Amiga and Atari computers. The “intelligent instrument” name refers to the program’s built-in knowledge of chord and scale convention and stylistic constraints. Automating these processes allows the user to focus on other aspects of the music in real time.
You can route the MIDI output (to your soundcard for instance).