Ok, an example: I rewrote PP&M's The Magi to keep all the imagery, and as many of the words as possible, but turn it into a solstice, natural-world, human-intellect paean (sp?] instead of a religious song. I called it The Magnon.

I call it rewriting. The Magnon is a secular version of The Magi, to me.

So in that case, Version works.

Now if I make a different song entirely but just use the tune, à la Master McGrath / Sweet Betsy From Pike, it is just another song To The Tune Of. Not a version of.

The Master McGrath that has an alternate tune is a version of Master McGrath. So same words different tune and same tune with [slightly but not completely] different words are both Versions. Do we need distinct terms for those? I like the idea.

So yeah, we need a term for To The Tune Of.