an answer to one of cristians points,a highly respected folklorist/ singer A.lloyd altered texts of traditional songs,see Jim Carrolls post.
in my experience traditional performers,have learned a song /tune often because they liked it . James Kingston a traditional fiddler, who I played with many times,had in his repertoire,Dashing away with the smoothing iron ,bluebell polka, mcleods reel, the blackbird,st patricks day,job of journey work,fermoy lasses,stack oif barley,.to him they were all tunes he liked,the origins of dashing away[he didnt know and didnt care about]likewise bluebell polka,categories to him as a traditional performer,were not important,what was important were whether people would like what he played and how he played,so there were inclusion in his repertoire of peices like The Minstrel Boy.
so as a TRADITIONAL PERFORMER[he learned all his music aurally]he had no television,only a wireless. but would have Putting on the Style[lonnie donegan] in his repertoire because people would have asked him for it[it was popular]the fact it was modern didnt prevent him playing it.