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.
Thumbjam - the holy grail of natural
Just wanted to share this. I've always been a sucker for brass and small ensemble strings and I have to say that for me thumbjam is a one stop shop for those. I had people asking me 'who' were the string section that play on my recording and brass just sounds so warm. Maybe not exactly hi if but definitely warm vintage. There may be other, probably more expensive emulations on mac and PC but IMHO this is the best thing on ios short of hiring the real thing. Thanks @Sonosaurus