A free app for Android, by Alexander Mishkovets.
My Piano Assistant is a free application that allows you to learn more about the piano, especially if you have never played it before. It is not only a reference book of chords (with all inversions), scales, and intervals, but also a user-friendly tool that can help you learn to play the piano and find chords on the keyboard. If you have never played before, it is a good idea to learn the basics first, and the app will help you do that. The application consists of 40 chords with all inversions, 170 scales, and 30 intervals, which makes it a comprehensive and very useful tool.
