(Benaroya) The musical family of which Loudon Wainwright is the patriarch is vast and complicated (and possessed of spooky, startling talent), and papa is a legend for good reason. Tonight he shares the stage with Dar Williams, and their combined wit and storytelling and tendency to overshare onstage should make for a diverting evening for folk enthusiasts young and old (given the venue, probably mostly old). Is that a little too short and sweet? Sorry. If you like this style of honesty-squared old-timey indie folk, you know and love these two more than life itself and are already biodieseling up the bumper-stickered Subaru. If you don't know these folks, it's because this ain't your bag, anyway.