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
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.
Cthulhu - VST MIDI-FX plugin for harmonic inspiration
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.