Documents by Readdle - A central hub for all your files.
Flowkey - The easiest way to learn piano with your iPhone or iPad
GoodReader - With GoodReader on your iPhone, iPod Touch or iPad, you can read virtually anything, anywhere.
Yousician - Learn to play music at home, at your own pace
OPlayer HD - OPlayer HD offers you a chance to play your videos and live streams as you like and directly transform your file in any format without any discontinuity.
Melodics - Melodics is a desktop app that teaches you to play MIDI keyboards, pad controllers, and drums.