Yousician - Learn to play music at home, at your own pace
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Synthesia - A fun way to learn how to play the piano.
Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
Playground Sessions - Online piano learning game.
Chordbase Lite - Chordbase Lite is a paperless solution for the gigging musicians to display lyrics and chords on mobile devices.