Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Audulus - A universe of sound at your fingertips - Audulus is a modular music processing app
Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Blocs Wave - A free audio app for creating music loops.
StepMania - Rhythm game for Windows, Mac, and Linux.
FL Studio Mobile - Create & save multi-track music projects on a smartphone