Rob Reiner’s 1984 satire on rock documentaries has the deadly verisimilitude of a Harvard Lampoon magazine parody: every cliche is in place, from the grainy kinescopes of Spinal Tap’s Mersey Beat beginnings to the rambling, vapid between-tunes interviews. The material is consistently clever and funny, though ultimately the attitudes are too narrow to nourish a feature-length film. Though Reiner has wisely introduced the elements of a plot toward the end (the breakup of the band as engineered by the lead singer’s calculating girlfriend), 82 minutes is still a long haul for a film defined only by derisiveness. The cast is largely composed of Reiner’s sitcom buddies, each reveling in the opportunity to be hip: Michael McKean, Harry Shearer, Christopher Guest, Howard Hesseman, Paul Shaffer, Fred Willard.