Four Chords was inspired by the song Four Chords by Axis of Awesome, which you can watch here:
It generates MIDI sequences that are surprisingly musical (in my opinion) for the simple set of rules that it uses. Four Chords does NOT produce sound, you must route the MIDI to another instrument.
The first 3 snapshots use the chord progression used in a staggering amount of pop music.
A video is available here, explaining all controls and features:
My recollection of music theory may be off and I did everything from memory so if you find mistakes with any scales or chords please let me know. If there are chords you would like to see added, please let me know the notes, I don't remember how to build 9th chords very well.
Four Chords was written in Reaktor 5.9 by salamanderanagram