“Air Guitar” is just one of four charming and comically irreverent vignettes from actor, film director, and writer Griffin Dunne. A self-consciously name-droppy account of his doomed romance with Julie Christie, this Single’s namesake and its accompanying slice-of-life essays mainly recount Dunne's pre-An American Werewolf in London days, when Dunne changed jobs as often as you or I change socks. In fact, “Radio City” clues everyone in on a rather ingenious, if morbid, way to find your next gig. You’ll also learn what not to buy when trying to impress your older girlfriend, a cautionary tale amusing to many, save Betsey Johnson. Dunne is at his best, though, in “Kennedy Letters,” in which a child’s need to be noticed eventually leads to a poignant presidential encounter… but not the one he expected.