Reaper - Reaper is a focused digital audio workstation (DAW) developed by Cockos. In the creation of the software, the digital audio technology company intended to make audio editing accessible to the masses.
Captain Chords - Write chord progressions in your favorite DAW
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
RapidComposer - MusicDevelopments RapidComposer: Music Prototyping and Automated Composition Software
Ardour - Record, edit, and mix on Linux, Mac OS X, and Windows.
Cthulhu - VST MIDI-FX plugin for harmonic inspiration