This is purely me thinking "out loud": A folk song is "rooted" in an area or location and develops, incorporating elements of the environs in which it is sung, heard and passed along. It is then "uprooted" to a new locale. The folk process continues, as names and places are adjusted to reflect the new locale in which it is again sung, heard and passed along. Is it the same song? 50 years later, how does the exegesis look?

On the other hand, movement of people from place to place has undoubtedly resulted in the melding of songs, as the melody of one is attached to the premise of another. Similar song ideas from different cultures often "cross-pollinate" (I happen to know for a fact that the Polish folk tune "The Too Fat Polka" was actually written about a girl of another nationality, which will remain unmentioned. But I digress.)It seems to me that "fakelore" is probably a lot more common than documented fact, when it comes to this.IMHO, the problem in establishing a songs roots beyond question creates a different kind of spaciousness than that referred to in the Heidegger reference above. There is, for example, a mythic space that a song like Tom Dooley inhabits that may be as satisfying in its own way as the geographic or historic.