Little riffs of comic genius can be heard amidst the heavy-metal cacophony of This is Spinal Tap, a hugely influential mockumentary about a has-been British rock band trying to squeeze out a few last drops of fame during a doomed American tour: bassist Derek Smalls (Harry Shearer) getting stuck in the giant embryonic sac he’s supposed to emerge from at the start of a concert; an 18-inch replica of Stonehenge being unceremoniously lowered to the stage in another botched number; guitarist Nigel Tufnel (Christopher Guest) bragging that his personalized amp goes “up to 11.” I could listen to fake documentary director Marty DiBergi (Rob Reiner, Spinal Tap’s actual director) interview the band all day. (Asked about the untimely death of their third drummer, Michael McKean’s David St. Hubbins says, “Dozens of people spontaneously combust each year. It’s just not really widely reported.”) Still, the music itself is brutal—whether you think that’s “the point” or a competent facsimile of what passes for good in the genre. I could watch Nigel complain about the size and shape of the catered sandwiches backstage all day, but a little bit of him whaling on his guitar goes a long way. The script (such as it was, as much of this was improvised) was written by Reiner, Guest, McKean, and Shearer.