I have finally "closed the loop" on something that Bad Mister suggested to me years ago on motifator.com, and then again here more recently. I now have a quick way of producing a "backup band" (drums, bass, rhythm tracks) for any song I want to work with.
I took a suggestion from that motifator.com thread and bought Band In A Box. All you have to do is type in the chord progression, and it produces the tracks for you. I export those tracks as a MIDI file, and import it into Cubase. Then I find a particular sequence of bars that seems suitable, and "Play" them into the Montage recorder the way Bad Mister described. Once I have them in the Montage recorder, I make User Arpeggios out of them. Then I can build a Performance that uses them, and use that "backup band" to play behind me on any song that I want. I've been trying to figure out a way to do this quickly enough to make it practical for years, and I'm delighted that (thanks to help I've gotten from a number of people) I can finally do it.
It leads to a question, though. I'm thinking I'm going to end up with a lot of User Arpeggios. What's the best way to manage a large set of User Arpeggios? All I can think of so far is a combination of using the category structure and some consistent way of encoding information in their names (similar to the names of the built-in arpeggios). I'd love to hear any other ideas people might have.
And a smaller question: when I created this first set of User Arpeggios, I forgot to set the category and subcategory for them. Is there any way to edit them and fix this? Or do I just need to re-create them and do it right this time?