There was an interesting programme by The Unthanks on BBC last night about British seasonal traditions it may be possible to get it back online or on catch up. They went from all hallows to Plough Monday and there are some great archive pieces. I recognised some very young friends with black hair from the 60s and 70s shots !!
I read that originally carols were communal dances with song

Incidentally a friend brought a musician,s tune book from the 1860s from Cumbria to the carols at Worrall. Julia Bishop played one on the organ which was a version of the Prodigal Son song.   They were beutifully written out dots and copperplate writing and the chap's name and date were embossed on the front.. The musician was a stonemason and the tunes were mainly sacred so it must have been very signifiant to him and his community. It was got off EBay.