Satirizing the Kingston Trio and New Christy Minstrels isn't exactly ripping from music's headlines. But topicality be damned -- Christopher Guest, Michael McKean, Harry Shearer, et al. put the hoot back in hootenanny with a 17-track retrofest that seriously outfunnies the folk-spoofing film. Not since Nashville has a cast so effectively written its own musical material. Numerous contenders vie for the ''I'm Easy'' memorial best song award; let's hope the Oscar goes to the faux Folksmen for their combined mining/train-disaster anthem ''Blood on the Coal.''