oh my god, dancers dictate, do you understand Dave, you are playing for the dancers, if they want to speed up or slow down they will say [in ireland]
.people don't expect their dances to change speed!" so in England why do callers ask to speed it up or slow it down dave[ they feckin well do]
and in ireland why do dancers ask, because they feel they can dance to it better at a different speed,
they rarely change speed through a turn or an a part, but often in England when the caller feels the dancers have got the hang of the dance they will ask the band to speed up a little. but generally when the dnce starts again
so you are playing for beginners in England, you start off slowly, when they have the hang of it you go a little faster if the caller asks for it.
for morris dancing, the dancers and the conditions[ grass or concrete] dictate the speed, plus the age and agility of the dancers.
in answer to your question, it depends on the type of dances and the dncers.
now polkas in england are quite different from polkas in ireland. the dance is different and in 4 /4 in ireland they are more like 2/4