Yes Diki, Roland used several different terms for the same thing. A User Program is basically a "registration," i.e., all of the currently loaded settings for tones, styles, status of the sync start, etc.

I'm not trying to load a whole set. Just merely to select a specific User Program from the set that's already loaded. It might even be enough to select the "next" one or "previous" one (a relative command.)

It seems like Roland generally used channel 13 as the "basic" channel, and there are only 16 to try, so that's not too daunting. However, it bothers me that the Prelude manual makes no mention of a basic channel. In order to receive User Program changes via MIDI, that parameter has to be turned 'on'. If there is no user-accessible parameter set for the basic channel, I'm not sure how I would do that.

I know for a fact that the G/E series can be made to do what I want, and the BKs also. The Prelude was an odd duck that was sold circa 2009, right between those other models. I'll be really disappointed if it turns out not to be possible. Open to other ideas...