Dick
The current version V5.11 of Murray's program lists the following compatible models:
Genos, Tyros 5, Tyros 4, Tyros 3, Tyros 2, and Tyros
PSR S970, S950, S910, S900, S770, S750, S710, S700 and S670
PSR 3000
Clavinova CVP309, CVP609, CVP605, CVP701, CVP705, CVP709
So, you are correct, compatibly starts with the PSR-3000 onward. The PSR-2000/2100, with their REG files are not compatible, but in Bill's case with trying to help his friend, there is no problem, as they are talking about converting from the PSR-3000 to a newer board. Even so, I have my doubts about how successful the conversion will work, as we are talking about converting from the oldest compatible PSR to the newest. That's a difference of 14 years, but at least they are going from an older board with lesser capabilities to a newer board with greater capabilities. Most of what works on the PSR-3000 should also work on the 975, while there are a lot of things on the 975 that would not even be recognized on the 3000. Still, I wish them all the best.
Roy