Remind me what a ‘User Program’ was again? Wasn’t it the same as a Performance is now? And a UPG on the G70/E80 series?

You often had to track the correct Midi codes for those in one of the sysex manuals or Reference Manuals.

One thing to always be aware is, there was never a code that changed the G70 era ‘User Program Set’ (UPS) or the BK9 series’ Performance List, so you could only select from what was already loaded.

Can’t help with the Prelude (never saw one ever!).

But to find the Basic Channel, try just resending the same command on Ch1, then Ch2, etc until you get a result…