Did you know about this phenomena? From the 14th to the 17th century groups of people would be gripped by a dancing hysteria, speaking in tongues and so on. Fascinating. Wiki on it here. People would play music along with the crazed dancers which only served to make it worse. According to another page The first major outbreak of dancing mania was in Aix-la-Chapelle in July of 1374. A group of people were seen to dance uncontrollably in the streets, foaming at the mouth and screaming of wild visions. They kept on dancing until they collapsed from exhaustion, but even then they flailed about in agony until forcefuly restrained. The dancing caught on, and spread rapidly throughout France and the Low Countries. There is a lovely poem there
Amidst our people here is come
The madness of the dance.
In every town there now are some
Who fall upon a trance.
It drives them ever night and day,
They scarcely stop for breath,
Till some have dropped along the way
And some are met by death
It sounds like some form of poisoning - some explain it as ergot - a fungus that gets blamed for everything from the Marie Celeste to the Children's crusade. I'm not sure what was going on but I think it would make a great movie...
Rethinking the Dancing Mania