Guitarix - Guitarix is a simple Linux Rock Guitar Amplifier for https://alternativeto.
Pianu - Learn to play the piano in your browser.
Ampire - State Space Modeled guitar amp/cab/stompbox simulator.
Flowkey - The easiest way to learn piano with your iPhone or iPad
TH-U - World class guitar amps and effects for PC and Mac
Playground Sessions - Online piano learning game.