I think the Church had a hand at altering and/or destroying anything that was non-Christian as they gained the spiritual foothold over the "heathens". Was it not the custom to sell real estate in heaven to folks on death's bed in exchange for their earthly holdings? What about the flaggellists who marched around beating themselves to gain entry to the pearly gates? Spanish Inquisition? Jacques DeMolay and the Templars burned alive and slaughtered? Childrens Crusade? The Church had an enormous impact on Northern and Western European culture and I don't think I'd be far off in suggesting that the people's songs were affected along with anything else they'd managed to invent to amuse themselves with that was not Doctrine. Correct me if I'm way off base, but I don't see how you will be able to.