Flowkey - The easiest way to learn piano with your iPhone or iPad
Pianu - Learn to play the piano in your browser.
Jameasy for Violin - Play rhythm game with a real violin. you can play with background music and real-time feedback
Playground Sessions - Online piano learning game.
alphaTab - alphaTab is a cross platform music notation and guitar tablature rendering library.
Simply Piano - Fast and fun way to learn piano