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.
Bs-16i playback troubles
I use bs-16i to import MIDI files and export audio tracks to GB to redo them or use some tracks outright (the instruments in bs-16i can sound very nice!); but I get to a point where the file won't play back, or will with no audio & I end up going through restarts and phone power-down/ups & load other files until something clicks. My first guess is that there is a CC command that's holding over and keeping other files from playing back properly, but I hope that there is a simple way to fix this without jumping through all the hoops...