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.
Xequence + Gadget - let’s talk
The one "multi-timbral all-in-one production combination" that I have extensively tested to be super-tight and hassle-free is Xequence + Korg Gadget. (No I'm not a Korg employee 
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@SevenSystems mentioned the above in a thread about Cubasis timing. I’d like to discuss this without totally derailing the other thread. How would I use Xequence + Gadget?
Comments
http://seven.systems/xequence/manual/#example-setups
"Using a multi-timbral app with multiple MIDI channels and sounds: Korg Gadget"
...has you covered! Let me know if there's any further questions or issues.
You set up your tracks in Gadget so that each track receives MIDI on a different channel. You then set up corresponding instruments in Xequence that send to Gadget.
To record the audio you can load Gadget as IAA in an app that records audio.
This is the setup that I use. It’s walled a bit, but I don’t have any timing issues, no mixdown issues or really anything except I can’t finish a dang song.
@Chaztrip the "Make song" button is being worked on, along with a "niceness" slider!
😂😂
Thanks all!
Seems like a topic for a future video.....