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.
New App - Aggregat - Reinvent Songs
Aggregat is a new app that let’s you break out stems of songs in what looks like a DAW timeline rearrange parts and add FX. Haven’t tried it yet but it’s free so will give it a go at some point. Cheers!
Edit - Probably not worth the trouble