Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.
Download on the App StoreAudiobus is the app that makes the rest of your setup better.
SpiralSet - no AB, but free for limited time
No AudioBus (at the moment, hopefully later)... interesting "sound toy".
Check out the video here:
Dev says: " SpiralSet is a soundtoy. The player tilts the SpiralSet structure to determine the motion and pathway of three light emitting balls. The movement of each ball controls the sound. Sound develops and changes in relation to the position, motion and pathway of the balls. "
https://itunes.apple.com/us/app/spiralset/id694667961?mt=8&affId=1678350&ign-mpt=uo=4