I think many of us who didn't grow up with our feet firmly planted in a tradition tend to treat it as an almost sacred thing sometimes - no changes allowed. I can understand that up to a point - we've got to be aware of what was sung and how, but when it gets to the point of pedantry, the tradition is no longer alive. We're singing and playing museum pieces, and we're re-inactors - nothing more.I remember someone talking about a traditional music singing session or open mike where nothing but traditional (old) songs were allowed. Fine - there are good ones and they deserve to be remembered, but it ain't traditional. I doubt the folks who sat around the fire at night and sang their songs ever said "you can't do any new songs or tunes." I think they were probably glad to hear one Uncle Hezekiah learned when he was up north working in the lumber camps, or one sister Sally learned when she was visiting her cousins over in the next county, or heaven forbid - one Billy-Bob wrote just last week. The same goes for instruments - I think folks just heard things they liked and tried them out. Sometimes if things were accepted by the group, they stuck.
I think snapshots are good at showing us what life was like, but people and traditions need to grow and adapt in order to survive. If we were to stop the music from changing, we'd be talking about it in only the past tense. I don't think it's possible for that to happen, though.