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.
GSi VB3m tonewheel organ for iOS
I'm excited that GSi is porting their tonewheel organ to iOS. I hope it's a stable release. I also hope it will be a success so they'll bring all their plugins to iOS.
I couldn't find it by searching in the app store, I followed the big iOS link on their home page: