Qsynth - Qsynth is a simple Qt4 application wrapper for the ...
Synthesia - A fun way to learn how to play the piano.
OpenMPT - OpenMPT is a popular tracker software for Windows.
Playground Sessions - Online piano learning game.
MilkyTracker - MilkyTracker is an open source, multi-platform music application for creating .MOD and .
Piano From Above - Piano From Above is a program that turns learning the piano into a videogame.