Flowkey - The easiest way to learn piano with your iPhone or iPad
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Jameasy for Violin - Play rhythm game with a real violin. you can play with background music and real-time feedback
Simply Piano - Fast and fun way to learn piano
alphaTab - alphaTab is a cross platform music notation and guitar tablature rendering library.
Real Piano Teacher - Real Piano Teacher is a music learning application that lets you learn how to play the piano, organ, flute, Guitar, and many other instruments just in seven days.