Esi2k here, soI don't know if it willl be relevant for you. The function i'm thinking of is "Channel Assignment" it's in the Dynamic Processing menu. Now, I haven't played with this so i'm not sure wich, but from what you say I'd try "Mono A-I: nine monophonic chanels. any voice assigned to the same letter interupt each other but does not affect other voices" So the manual says
Might not be very usefull since it's not the same machine, but you should have something similar..