For myself, I just like to sing. If I hear a song, even an old song, done by a contemporary artist, that not only moves me but feels like something I could make my own, then I go for it. (Not being a public performer, I don't have to worry about infringement rights, but then, I never try to copy the way someone does a song anyway). Indeed, if the performance is strong, I might wait for some months, even years, before I tackle it, to be out from under the influence of that first experience.

If the story in the song really interests me, or if I dont understand the words, I will go on a hunt for source material, but ... sometimes not. Phillistine that I am, I don't even always like the Carter Family all that much.   Source material is intersting, but to my ear is not always musically satisfying. I value the old "source" records I have for their authenticity, but I don't really listen to them all that often. Once I get interested in a song, and start playing around with it, I don't WANT to hear other versions...at least until I've found my own.

It is important to me, on contemporary music, to be able to credit the writer, even in informal settings, as a matter of respect and courtesty. And I try to get time frame and origins reasonably factual for old songs, just to put them in context. And if someone should ask if there really was an Mary Hamilton, it's nice to have some kind of answer...altho from what I've read it wont be entirely satisfactory.