What are some alternatives?
When comparing Songs2See and Flowkey, you can also consider the following products
Pianu - Learn to play the piano in your browser.
Simply Piano - Fast and fun way to learn piano
Playground Sessions - Online piano learning game.
Synthesia - A fun way to learn how to play the piano.
Skoove - Babbel for learning the piano
Yousician - An interactive guitar-learning app.