Yes Helen, and the question is when THAT musician who's soloing speeds up (or slows down) what do you do? Do you try and "fight" him/her? or do you follow them no matter what? The latter of course if you're in a live situation. If you don't then everything can collapse and everyone on stage will look like idiots.

There is a Jerry Douglas album (very well-known session dobro player) where they do a tune called "Monroe's Hornpipe" and the tune moves along at a nice clip, with the tempo nice and even, as the various instrumentalists in the band all take their turns soloing, and then finally Jerry takes his. In the midst of his fanciness, from the get-go he speeds up like crazy, and the rest of the band just matches him.

Now, if I'd have been the producer of that album, I wouldn't have let that take make it onto the album. I would have had them redo it and told Jerry to keep it steady when he comes in. But, perhaps the actual producer of the album (maybe even Jerry himself) liked the energy and kept it for that reason. You can have both - energy and a solid tempo, but of course there are always exceptions for whatever the reasons. My regemented ears happen to prefer a consistent solid backbone holding things down, unless we're talking avante guard or fusion jazz, with all sorts of polyrhythmic elements playing off of each other.

Then there's Willie Nelson's band trying to follow Willie....but I think this has already been covered in a fairly recent thread.