It's not a midi interface but a patcher noon.
If you have such multiple keyboards with multiple expanders you can connect them as you wish.
Personally I have two master keyboards (DX7 + RD300) and two expanders (U110 + 05rw) + pc.
4 midi in (ABCD) and can also group A + B
8 midi out
32 memories config

UTILIZATION

I repeat this is not a midi interface
IT'S A patcher

OVERALL OPINION

has been 15 years since I
is very simple
it works always
I had occasion to pay 500f epoque
IS IRREPLACEABLE