Found it (after struggling). Here's how:

1. Go to PGM support, patch maps
2. Find Ketron SD2 zip file and dl
3. Go to your RB folder and rename patches.ini to something else (patches.old, for example)
4. Copy the patches.ini file from the Ketron SD2 zip to the RB folder
5. Load a file with midi
6. Right click one of the midi tracks and select "patch select dialog"
7. Pull down "patch list" and select Ketron SD2
8. In larger window you'll see the 'main' patches and in the variations window the variations on that patch.
9. click the voice you want and click ok
10. I think that works