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 Store
Audiobus is the app that makes the rest of your setup better.
An AUv3 that could do Frequency Modulation with any source audios
Wouldn't it be neat to be able to send source audios and then structure them with FM algorithms, having them modulate each other in different orders? So you'd have one synth, send its waveforms to be modulated by a different synth, and so on. I'm probably missing something here with it either being very difficult to accomplish, or already done.