What do model train sets, the Jewish Children's Polo League, Sure-Flo incontinence supplies, the vibratory power of colour, and an abortive TV comedy show called 'Wha' Happened?' have in common? Not a whole lot, beyond rubbing shoulders in Guest's deadpan pageant of sub-cultural quacks and quirks. Reassembling the superb improvisational stock company behind his community theatre spoof Waiting for Guffman and dog owners' parade Best in Show, A Mighty Wind finds Guest trout tickling in a musical milieu again, some two decades on from Spinal Tap. Indeed, the twee folk trio he, McKean and Shearer inhabit - The Folksmen - could almost be Tap's fusty flipside, with male pattern baldness in lieu of foil-wrapped love pumps, but a comparably bare-boned back catalogue. Even more dilapidated is Mitch, of ex-lovebirds Mitch and Mickey (Levy, overplaying his hand a jot, and O'Hara); a public break up and private breakdown have left him in a semi-vegetative daze - a world away from the implacably perky New Main Street Singers, with their overprocessed minstrel harmonies. Gathering for a PBS concert showdown in honour of their late agent, the three outfits relive old memories and demonstrate the attrition of years. The heart of the film is as much about the pathos of ageing as the comedy of aspiration. At times even the laughs seem to be thinning in empathy, which may explain Guest's stockpiling of ephemeral delights around the margins: Willard's breathlessly self-amused former stand-up, Coolidge's exotically dim PR, Begley's Jewish-slang-dropping Swedish TV exec.