actually I have found that many of the older songs seem quite secular in nature...especially those which praise some of the more rural customs of wassailing, etc.

I am curious as to the evidence which suggests that old songs were altered to include more religous lyrics with the passage of time; much like many old Scottish herbal charms had saints' names added over the years...

any thoughts? I bet Ronald Hutton addresses this somewhere, I will look trough his books...