Learn to play piano by ear within weeks. 10 to 15 minutes each day (or however much you like) and after 1 week you will already gain powerful results. Learn to play both melodies and chords. These skills transfer very well to all the other instruments. Also works very well as a portable fun piano for quick ideas. To start ear training just press "Play" and repeat what you've heard. Then increase the level. Change major to minor and later try chords! This app suits well a complete beginner but also an experienced musician to perfect relative pitch hearing.
