M. Ted, I actually commented on scales and modes, which can theoretically be separated, but sometimes the distinction is not clear. E.g., if someone always plays the 7th somewhat flatted, is it really just a slight aberation, or is it flatted enough that the tune should be called mixolydian rather than major?

The point of collectors' notation of tunes- most collectors of such are well aware of modal structure, and that's not the problem. When a collector notes down a tune in conventional notation and we see his/her noted version, we don't know what scale the collector actually heard, probably just intonation, I think, for vocal melodies, but when we play it on a piano it comes out equal temperament, or by a good fiddler, just intonation.