I also wonder about the size of some of the dance parties of yesteryear. The most recent time I played without benefit of microphones was at a re-enactor's ball at Ft. Osage near Kansas City, MO. We were in the attic of one of the museum's buildings which had log walls, bare rafters, and a wood floor. I don't think there were but maybe twenty-five to thirty dancers all told. The caller was knowlegable and experienced, and called without a mic. We musicians did fine. We had two fiddles, a hammered dulcimer, and a guitar, maybe. (It has been a couple of years ago.)
Jim