Besides recommending the works of Ronald Hutton, I wish to point out the error in the notion that the only written sources for paganism are modern. The poems of Hesiod, the hymns of the RigVeda, the votive inscriptions of the Romans, the speculations of the stoics and neoplatonists, should be considered, at least in the first analysis, equally as 'pagan' as, say, the unwritten lore of the druids or the of the mask societies of the Senecas and Onondogas.
Be very cautious of assuming great antiquity for any music or dance that was not documented until modern times. The only western European music which can be said to have passed down from the low middle ages with only minor changes is ecclesiastical chant. I would doubt that any still-practiced folk-dance's choreography was more than a few hundred years old, unless you want to define the choreography in broad general terms. Dancing in a ring is indeed a very old practice, but any specific ring dance that is still danced is probably nowhere near as old.