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 StoreAudiobus is the app that makes the rest of your setup better.
Comments
As a stereo mix or as 6 separate tracks in AUM?
I have different MIDI controllers with pads, faders, pots and encoders but the only one I'd recommend getting is the Keystep (or any other controller keyboard that fits your needs).
Except you're using GR16 on a phone, turning knobs on-screen works very well and as most functions cannot be remote-controlled, you'll never be able to stay away from the screen like you would with Ableton Push 2 or NI Maschine.
If you really want it anyway, make sure the fader/pot controller can send MIDI CC on different user-configurable channels and the keyboard of choice supports easy and fast switching of the MIDI channel to send to, otherwise you'll have a hard time using MIDI POLY mode which is required if you want to control e.g. volume, filter cutoff and pan on different channels.
My choices in that case would be Launchpad Mini and Launch Control XL, or AKAI's APC Mini.
And don't expect endless encoders to work as intended, our favorite apps don't support relative MIDI CC.
only stereo, or 2 mono,