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.
iOS 12.4: Taking stock
I'm trying to get a handle on all the foibles of iOS 12.4, as I'm getting the impression it's more than what I'm personally seeing. For example, I've heard reports of GarageBand freezing or recording silence, which is something that I've not seen myself.
If you've got 12.4 installed and you're seeing oddness, would you leave a comment below describing what's happening for you? I'd like to make Apple aware of as much as possible, in the hopes that 12.4.1 will solve everything (because 12.3.x has its own issues!).