As it happens, I've just been reading a new book on Welsh folk song (Welsh languag) and it says (in translation):

Twmpath is another word connected with sports and dance and all kinds of merriment. There is a description from eastern Montgomeryshire where the playing mound ("twmpath chwarae") was opened with considerable ceremony and gaity on May Day eve. The twmpath was located on a hill or raised area near the village. A flat strip was prepared there and a mound of earth created for the harper or crythor/fiddler. (see thread on Crwth) It doesn't take a lot of imagination therefore to see from whence comes the term "twmpath dawns". (from "Cerddoriaeth y Cymry" by Arfon Gwilym)

Just thought that was more grist to the mill. I didn't know the bit about a twmpath-upon-twmpath so you learn something every day!

sian