WolframTones - Listen to what I just found in the WolframTones music universe
Odesi - ODESI is a music sketchpad that exports your projects to Audio and MIDI.
Abundant Music - Generate royalty free music with a simple but very powerful procedural music creator
RapidComposer - MusicDevelopments RapidComposer: Music Prototyping and Automated Composition Software
AthTek DigiBand - AthTek DigiBand is a piece of automatic music composition software for Windows.
Captain Chords - Write chord progressions in your favorite DAW