What are some alternatives?
When comparing Yousician and Synthesia, you can also consider the following products
Simply Piano - Fast and fun way to learn piano
Flowkey - The easiest way to learn piano with your iPhone or iPad
Playground Sessions - Online piano learning game.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.
Pianu - Learn to play the piano in your browser.
TuxGuitar - A Multitrack tablature editor and player.