Odesi - ODESI is a music sketchpad that exports your projects to Audio and MIDI.
Captain Chords - Write chord progressions in your favorite DAW
Cthulhu - VST MIDI-FX plugin for harmonic inspiration
Harmony Improvisator - Harmony Improvisator is the most advanced harmonic composition tool on the market.
Hookpad - Web-based music composition that greatly simplifies writing chord progressions and melodies
Band-in-a-Box - Band-in-a-Box is so easy to use!