Thanks Bill. Roland was on the forefront of MIDI development in the late 1980s, and it's well-implemented in many of their keyboards. As I said, I have direct selection of specific user program(s) working on the E-50 and the BK's so I know that it's possible on at least some Roland models. A thorough reading of the G-800 manuals suggests that it's possible on that generation of TOTL keyboards as well, although the starting memory address and sample commands are not given in the manuals (as they are with the G-70, E-50 and BK's.)

If someone has actually figured this out for the Prelude / GW-8, those are the parameters I need to know. Thanks!