Hi,
that sounds like an interesting scenario. Don’t know much about organs, I gather upper and lower keyboards would send on 2 seperate midi channels? If so, one would assign the lower key bed ? to have the split for left hand arranger chords, other side of split for melody, and the top set of keys for melody.

Actually if one had the space to be able to do it , an L shape configuration like I initially had with my sx900 would work perfectly.
Ie Organ ( my p121) at front sx900 to the side. The sx 900 is used as a module rather than as a keyboard. The sx900 has the registrations so they could be set up for individual song, it also has the registration sequencer, so the the registrations can be saved in the order required for the song, so a simple tap on a pedal, and it just walks it way thru the registrations. Basically no need to touch the sx whilst playing a song, only need to touch it when choosing the next one.

That’s how I originally had my sx/p121 set up. Unfortunately the p121 didn’t have audio in, so I needed a pair of speakers on either side of the piano.

Just another option maybe, Lee.

Probably in hindsight I might have bought a fully weighted keyboard controller ,with aftertouch ( if there is such a thing) but when I bought the p121 , my intention was not really to use it as a controller. The p121 was initially just going to be used as a piano in the living room. The sx was in my bedroom/studio. But after Dave mentioned it made such a difference to piano sound on sx, my plans changed.