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.
AWARE? ORIGINAL AU's FAVES for me! BLAM!!!
These were literally one of the first AU FX apps and still remain a go to for me.
Universal. Cheap. QUALITY!
Also, they have the key features easily displayed for those of who like performance style use and easy enough parameter GUI for easy mapping on the fly.
I know some people are a little newer to this so wanted to point out some effective quality and value priced options for pro iOS music production!