Simply Piano - Fast and fun way to learn piano
Pianu - Learn to play the piano in your browser.
Yousician - An interactive guitar-learning app.
Guitar Pro 7 - Create, play and share your tabs
Flowkey - The easiest way to learn piano with your iPhone or iPad
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.