Jim Dixon - I've noticed that very same thing, a gradual speeding up on old 1920's recordings. And, Don, I wondered too if it were the band or the recording technology.
My guess is it's the band. They sound somewhat tentative at first and then seem to get into a "groove" and rip on down the road - especially fiddle and banjo groups.
It sounds like a lot of good advice re the click track thing. The little experience I've had, we always tried to lay down a bass and rhythm guitar.