MOTU Digital Performer - Get inspired, then refine your mix — all in a singular workflow.
Synthesia - A fun way to learn how to play the piano.
FamiStudio - FamiStudio is very simple music editor for the Nintendo Entertainment System or Famicom. It is designed to be easier to use than FamiTracker, but its feature set is also much more limited.
Piano From Above - Piano From Above is a program that turns learning the piano into a videogame.
SunVox - SunVox is a small, fast and powerful modular synthesizer with pattern based sequencer (tracker).
Playground Sessions - Online piano learning game.