Please excuse my necromancy on this thread, but I do not understand how to access the NRPN messages.
The NRPN support in Duplex is essentially a “short circuit” that intercepts those messages and allows you to control effect parameters directly. So you shouldn’t need to specify anything in the controlmap really, since it isn’t a full implementation. I haven’t got an MPD32 myself, so I have never actually tested how well it works
Butin this reply, I’m talking about how relative message support was planned - this has been implemented in Duplex for a while now, along with support for 14bit pitch bend message (which happen to be very similar to NRPN messages). But “proper” NRPN support is still missing…