I was reading a thread on Jane Austen era dancing and found this:

Well, for the Regency era the dancES vs. dancING distinction is not quite as large or universal as it appears. The supposed names of (country) dances in many cases are more likely the names of the dance tunes, with the figures being fairly interchangeable – the same tune could have many different figure combinations, and the same figure combinations turn up linked to many different tunes. Linking specific figures to specific tunes of this era is something of a modern artifact, not necessarily reflective of the historical experience. (And of course one could always just compose the figures on the spot to any tune desired – there are surviving manuals full of rules for how to do it (emphasis added). It’s quite a trip to do this with a roomful of modern dancers!) But you could be quite good at country dancING without knowing any particular country dancES.

I wonder who composed the dances on the spot? Did they have a caller, perchance?