In terms of the famous "folk process", of course, the question is irrelevant. But it could be hugely important, as implied by MMario's post, where a "version" becomes copyrighted and commercially successful. As an example, Pete St. John's "version" of "Fields of Athenry" is a copyrighted knock-off of a trad song dating to the 1880s, with no recognition of that fact given. Or Elvis Presley's copyrighting of the melody to "Nora".