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.
Public Service Announcement: If possible, always install Audiobus compatible apps wirelessly.
If possible, always install Audiobus compatible apps wirelessly. Don't use iTunes on your Mac/PC. That way you'll always get the latest version.
(... at least until Apple's servers are still delivering the older version, because the update was very recent.)