What are some alternatives?
When comparing Flowkey and alphaTab, you can also consider the following products
Simply Piano - Fast and fun way to learn piano
MyMusicTeacher - MyMusicTeacher is an excellent music learning application that allows you to get access to its revolutionary guitar lessons, from beginner to an advanced level.
Synthesia - A fun way to learn how to play the piano.
Guitar Pro 7 - Create, play and share your tabs
Pianu - Learn to play the piano in your browser.
iReal Pro - iReal Pro – Music Book and Backing Tracks is a commercial music app developed by Technimo for Android and iOS devices.