Sharing the answer from AJ, Mystery solved :-)

It is capable of doing this .

Each style can save up to 4 voices per Arranger part.
- pick style you want to modify
- go to style mode.
- go to page 2/2
- A-D on left side (F1-F4) represents the voices assigned to the parts. So press F1 and pick a voice for a Arranger A. Repeat for the others.
- F5 turns this feature on/off for this particular style. Turn on.
- F10 turns on this feature globally for all styles. Turn on.
- when done, press save and save style.
- exit, press save and press custom start up so these setting are recalled each time the keyboard is turned On.

Thanks. Please post this response on SZ

AJ