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.
Funny way to play a midi file : the tunnel notes of piano 3D (massive technologies inc)
This is an amazing realistic piano keyboard with all camera 's points of view and midi in and out,IAA and AB ,a good way to learn the instrument with both hands and this fantastic tunnel notes for live performance or funny controls with inertia of a midi files.This app has a subscription but you can test it for free (i am not affiliated with it)
In the same spirit there is also synthesia for playing and learning songs but without this tunnel notes.