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.
VisualSwift now supports hosting AUv3 Audio Unit Extensions and AUv3 Effects with Multi-output
This might be of interest to some.
VisualSwift is an iPadOS tool for creating apps quickly without requiring coding. After creating an App visually, swift code can be generated and exported to be included in an Xcode project and built.
A test version is available through TestFlight, link on their website.
Some videos here:
Hosting Auv3 Audio Unit Extensions
Hosting Auv3 effects with multi-output
How to create a software synth