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.
How can I crossfade two audio tracks and automate the fade?
Preferably in Cubasis but if you know a technique in another environment, let me know. I know how I'd do this in Reason 12, but for iOS I'm drawing a blank.
I have two audio tracks that I want to fade back and forth between. I'd like to be able to twist a knob or push a slider to blend between the two seamlessly. Then I'd like to automate that knob/slider to either program (or "play" it line and record the automation that way).
Any ideas?
Comments
Drambo ( automation )
Aum ( no automation )
Map 2 tracks to a midi fader or app fader.
Reverse polarity of a mapping.
Make busses. So the faders can be full but the outputs set.
Maybe KQ feedback app to send the tracks to cubasis. Where effects will be.
Found this for AUM

You can easily do it in AUM using FAC Envolver on a slave fader to invert the output of the control fader.
MIDI mixer in AUM?
https://apps.apple.com/us/app/midimixer-for-aum-auv3-plugin/id1542209150
That looks promising ๐
That will definitely do it, thereโs a few options or ways to go about it. Particularly in aum.