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 StoreAudiobus is the app that makes the rest of your setup better.
RMX 1000 - Anyone still using this app?
Just watched @thesoundtestroom video which was great ——> 
Wanted to see if people are using this or having any success with it. $20 so need to do my homework first!
https://apps.apple.com/us/app/rmx-1000-for-ipad/id1035498886
Comments
Have you checked the reviews on the link you linked to?
I have and they’re pretty outdated