Performance Merge is exactly what you want to do.

The only requirement to begin customizing and merging Performances is you have to be able to count to 8. 😉

Call up the PERFORMANCE you want to start with. Let's say it occupies 3 of the 8 slots... you can press the "+" (add) icon in PART 4 or [SHIFT] + [CATEGORY] to activate the "Part 4 - Performance Merge" screen.

Now you can Search the Montage cloud, for the second Performance... Blue are Multi Part, Green are Single. You can set your search Bank and Attributes to narrow the options.

If you add a PERFORMANCE that is more than 5 PARTS only the first five will be added to your 3 under "Keyboard Control". (The others will be added but not under your control). If you wish to add just a specific PART of the second PERFORMANCE you can set the SOURCE parameter on the top line to select just a particular individual PART of another PERFORMANCE.

So it is possible to bring any PART from any Performance into your current PERFORMANCE.

I've just discovered what a powerful tool Performance Merge is. Testing the instructions above,I just merged two performances, changed some of the arp assignments, and voila - a brand new new, useable sound. Amazing!

Thanks BM, one thing this is a little strange is this statement "The others will be added but not under your control". Is it just that the Montage can only handle 8 parts at a time so the remaining are added and wont sound? I can see where combining performances could be limited because a lot of performances are made up of multiple parts and those parts are crucial to the overall sound.

Thanks everyone,

Please excuse the "timeline" of this post, as have I figured out a workaround while double checking before I posted.
I'm posting in case anyone else runs into this.

Does anyone know of a setting, etc. that would prevent multi-part performances from merging all of their parts when trying to add them to an existing performance?
What am I trying to do:
I am starting with a 3 part performance, (*!) This is a simple E Piano / Synth Lead Split El Piano is shifted +12, and a full rang version of the EP that unmutes with scene 8.
I want to combine it with a 2 part performance, following the usual procedure.

(here is the answer to the question before I ask it!)
Parts 3-7 are open, part 8 is a copy of the El Piano, but no note shift, and full range on the keyboard. It's muted in all scenes except for 8, (hit scene 8, and I have just E.P. full keyboard.) IT WAS ENTIRELY ARBITRARY THAT I PUT IT IN PART 8.
pressing the"+" button in the next open part (3)
when I select a multi-part performance, (in Blue), I only hear part 1, and if I hit enter and look at the home screen, only the 1st part is merged..

The answer:
Even though there were enough open slots (3-7), having a part in slot 8 seems to prevent multi-part performance from being merged.
i copied the part from 8 to 3, deleted 8, and now I can audition and merge multi part performances with this performance.
So, no more putting a part in 8 until the others are populated.

I have to learn a lot of tunes each week, and need the sounds to go with them, lined up and ready to go!
This is why I really appreciate the the power and flexibility of the Montage!

...now back to playing the Bosendorfer with the CP4 as controller....(thanks!)

Happy New Year!
Lk