Dick, I don't think changing the way a tune is played is necessarily a discourtesy to the composer. Are the various "versions of "The Sweetness Of Mary" that I quoted in my initial post discourtesies to Joan MacDonald Boes? Particularly when, according to various sources, Jerry Holland's version, which departs from the original tune structure, is seen generally as the "definitive" version.

For a start, the composer may not have recorded or played their composition in a live situation themselves, so we start from the dots and do with them as we can. What's a "moderately slow" strathspey, for example? (the tempo instruction on my copy of the sheet music). You can hear Jerry Holland's speed from the link in my original post. You can see and hear my humble version (recorded yesterday) here. I play the original structure at what I consider to be a "moderately slow" speed. Which is the better version? One guess!

You mentioned rewriting "Masters of War". well, this thread is specifically about tunes, not songs - and the whole point was to make a comment that melodies, even modern composed ones, can undergo subtle and not so subtle changes with time and with no-one being particularly worried about that process. Horses for courses. You can't stop performers doing what they will in their own style with a tune - and why should they? If it has any validity, others will join in and the tune will flourish. If it hasn't, then the version will probably wither away. The point is, there's no fuss over the process - the modern tunes, changing here and there, sit happily alongside the "anon" tunes in sessions and singarounds, etc.