‘Fiddlesticks!’ you say!  Yes, that’s the name of the technique used here in this performance of “J’ai ete au bal” (“I went to the ball”).  Dewey Balfa fiddles and sings, and his nephew Todd Balfa lightly strikes the violin strings with two sticks, as Dewey plays.  There’s a recording of this on the CD Dewey Balfa and Friends.  This is an amazing technique in appearance and in sound.  Wonder how someone thought of this?