I’m not sure exactly how you’ve constructed your piano performance. I can guess - but may not be accurate what you’ve done. You could upload an X8B - which would detail your Performance - but it would not take much time to describe what you did similar to:

1) Loaded "CFX Stage" - a single PART piano.
2) Changed "CFX Stage"'s ARP 1 to "FA_Bomba_C" changed ARP 2 to "FA_Salsa 2_N"
3) Turned on PART zone control ON under "Zone Settings" menu and changed "Octave Shift" in this same menu to +2

Where you start with a preset and describe how you “build” the resulting Performance step-by-step.

I’m assuming you have PART1 and PART2 with the same piano and I have to guess you have ARP1 and ARP2 on both piano PARTs and each matches (ARP1 is the same ARP1 on both PARTs) and that ARP1 or ARP2 is the Bomba ARP for both PARTs and the Salsa ARP uses the other ARP slot (ARP1 or 2). And that PART1 and PART2 are offset using “note shift” by an octave.

I’m not sure what’s not working on your end (what you are listening for), but when I do the following:

1) Loaded "CFX Stage" - a single PART piano.
2) Changed "CFX Stage"'s ARP 1 to "FA_Bomba_C" changed ARP 2 to "MB_Salsa 2_N"
3) Turned on PART zone control ON under "Zone Settings" menu and changed "Octave Shift" in this same menu to +2
4) From HOME - touch PART1, choose “Copy” from left-hand pop up menu, then set destination of copy to PART 2.
5) Modified PART 2 to change common PART parameter “Part Settings” -> “Pitch” parameter “Note Shift” to +12 or +24. +24 makes the Salsa ARP sound closer to matching Bomba - but that is to taste.
6) An optional change - on PART 2 (the octave shift piano) I chose to change ARP1 (which was FA_Bomba_C) to “Mute 4/4”. The reason for this is that the “Bomba” ARP is already an ARP with octaves in the pattern. You may or may not want to add the additional PART2 octave notes to Bomba as well - so this is optional. If you do not do this step, then step 5 should likely be set to only +12 and not +24.

When I use this Performance it seems “correct” to me - but I am not the final arbiter.

okay! my PERFORMANCE settings:
Part 6: "House Piano" "Note shift" +12
Part 7: "House Piano" "Note shift" +24
BOTH PARTS:
Arp1: MB_Salsa 2 _N
Arp2: FA_Bomba _C
Note Limit (Arp): C1-A2
Octave Shift +0
Octave Range +0

When in Part 6 I change the settings zone "Octave Shift" to +2 the part stops playing, and when I do it in part 7, there is simply no difference in sound. Nothing happens.

6) An optional change - on PART 2 (the octave shift piano) I chose to change ARP1 (which was FA_Bomba_C) to “Mute 4/4”. The reason for this is that the “Bomba” ARP is already an ARP with octaves in the pattern. You may or may not want to add the additional PART2 octave notes to Bomba as well - so this is optional. If you do not do this step, then step 5 should likely be set to only +12 and not +24.

I'm sorry, but I do not find it done to change the "Mute 4/4" parameter, or I do not understand what you mean.

Everything else I've tried and it's still working, since the Arp MB_Salsa _N drops too much octave.

Do not know how much I appreciate the inconvenience that is taken to help me.

Thank you!

"MUTE 4/4" is the name of an arpeggio - just like "FA_Bomba_C" or "MB_Salsa 2_N" are also names of Arpeggios. What I did was go into the common "Arpeggio" -> "Individual" screen for PART 2 (which for me is the +24, 2 octave above piano) and replaced the "FA_Bomba_C" ARP with "Mute 4/4". When you touch on the "FA_Bomba_C" name inside the "Arpeggio" -> "Individual" screen, a menu will pop up to choose an arpeggio by name or by number. I choose by name. A new window is shown which is the Arpeggio search screen. There is a magnifying glass in the upper-right where you can type in a partial name. I usually type in "mute" and then all of the various Mute arpeggios are shown. They are in different time signatures. The original ARPs are in 4/4 so I picked "Mute 4/4". What this does is plays silence for the 2nd piano only when you pick ARP 1 - which for me is the Bomba arp. This is because, for me, I did not feel the Bomba arp needed octave doubling. But this is your choice.

I've tried it, and I'm not convinced by the piano alone without octave. I will stay with the desire to hear that pattern in a "natural" octave. Nothing happens, I have chosen another pattern that is "in place" and I will solve it like that. Jason and Bad Mister, enormously grateful for your help.

All my gratitude!