This may be a somewhat goofy reflection, but;
Art had "This machine kills time" on his banjo head. Obviously the inspiration from Woody's "This machine kills fascists" was there, but I would suspect Art did it primarily as a gentle joke. I wonder if even Art himself ever thought of a deeper implication that I find quite appropriate: Few have been as dedicated as Art to keeping the treasure of older folk material alive. When he performed, we became "unstuck in time"; the time between the creation of the song and his performance of it effectively ceased to exist for us.