Way back in the 60/70s it was far more clearly defined. A "traditional" singer was one whose repertoire came from their life and family. We were the "revivalists". Now, with an obviously ever-decreasing pool of "traditional" sources, revivalists are increasing termed "trad singers".

However, "sources" are different too. There is, of course, Voice Of The People and massively important recordings of that ilk. But sources to today's younger performers are, ever-increasingly, revivalist: their parents' vinyl and Waterson:Carthy etc boxed set reissues.

If you think "source" is too prescriptive you could always use "song carrier". Doesn't cover the tunes though . . .