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.
Loopy Pro Questions
Let's use this thread for people to post "how do you do that" type questions. It'll be useful to know what sorts of tutorials would be useful (hint, hint to those of you who can make some quick helpful demos) and will be useful in beefing up the Loopy Pro related pages on the Audiobus Forum wiki:
Also: take a look at the wiki if you have questions. They may already be answered. @tja posted a handy PDF there with screens from the built-in tutorial.