Thank you for the reply.

The tracks are not frozen, and I do make the songs seveal chourses long. Some tracks seem to have variations and some literally play the same 2 or 4 bar figure all the way through. The Floyd Cramer piano track is a perfect example. Floyd created his signature piano style bu playing little upper-register tinkly fills. BB's floyd track generated exactly one version of that kind of fill. I took it into sonar and modified about 60% of them to get some sensible variations. Pretty tedious.

And regenerating the song did not improve things.

From the paucity of replies, I have to infer that this is in fact the way BB works, and my initial impression was wrong. Disappointing.