Keezy Drummer - Make a beat in seconds
ChordIQ - Learn notes, chords, sight reading, perfect pitch and more.
Sampulator - Make (and record) beats on your keyboard
soundrop - Soundrop is an app that allows you to create your own personalized sound track to keep you focused or relax.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
muted.io - A magical collection of interactive music theory tools & visual reference pages for musicians and music producers