Phil said
".... and tunes like Black Joke which have a 4-bar A and 8-bar B - and presumably should be played AAB or AAAABB... and on it goes. Fascinating stuff "

But it depends on the dance. Here is Earl of Stamford dancing a stick dance with a short figure (different each time) repeated, and a longer chorus repeated. So played AABB (and there is an extra 2 bars of stick clashing at the end of each phrase - the As are 6 and the Bs 10 so you'd be hard put to make a 32 bar tune.)Also Travelling Morrice dancing the Adderbury hankie version and Ilmington performing a clapping dance, same structure (with a pause in the chorus).

Some of the Morris dances have a part where two dancers on a diagonal dance together, then the second corners do the same, then the middle couple repeat e.g.Deer Creek dancing Banbury Bill so need AABBB
Or you might have some fancy work where part of the B music is played at half speed (the 'slows') so that the dancers can leap higher or get down lower.


A lot of the Playford tunes have a short A and a long B and are usually danced AABB, though the version of Jamaica we dance (and the song that is sung to that tune) needs AAB.
Near downfall of a caller - my Country Dance Tunes book (Cecil Sharp) had the short As printed twice to make an 8 bar phrase. So I asked the Forlorn hope to play various dances "24 bars, one A two Bs" The version they were playing from had 4 bar As so it didn't add up, and fortunately they noticed that.