Granny Smith - Granny Smith is an Addictive, Action, Puzzle-Platform, Side-Scroll, and Single-player video game developed and published by Medicore.
Flowkey - The easiest way to learn piano with your iPhone or iPad
Megatroid - Megatroid is a gorgeous, Action-Adventure, Puzzle-platform, Side-scroll, Sci-fi, and Single-player video game developed and published by Triolith Entertainment AB.
Yousician - Learn to play music at home, at your own pace
N++ - N++ is a Puzzle-Platform and Single-player video game that takes place in the 2D world, developed by Metanet Software, Inc.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.