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.
Question to iPad users...
I still thinking to get one of these things (but i still like the smartphone size more). I have a question... I had problems on the phone with 64GB space. When i now use a iPad with retina with 128GB i'm not sure if it's enough then. Beside all the music apps i want some games, videos etc. on it. The iPad has 4 times more pixels as the iPhone, so are the apps there much bigger? Just curious about it. Thx for answers!