FL Studio Mobile - Create & save multi-track music projects on a smartphone
Flowkey - The easiest way to learn piano with your iPhone or iPad
Splice Beat Maker - Make and share beats in your browser
Yousician - Learn to play music at home, at your own pace
Type Drummer - Drum by typing
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.