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.
Interviews with iOS music app Developers
I would love to listen to an interview with an iOS music application Developers who would tell how theirs applications are created, from where their ideas come from, what are the biggest problems building an app and how are solved, how is teamwork arranged, how does the cooperation with Apple look like and other interesting facts from the developer's life
In the next comment I posted what I found. If anyone know another sources please add it to this thread. I will transfer it to wiki and try to keep it up to date. Thanks in advance (I hope to update some dead links on the forum in final wiki list)
Link to WIKI: Interviews with iOS music app Developers