In ''Waiting for Guffman'' -- that light tragedy of Broadway-size ambitions and Main Street-size abilities -- director Christopher Guest clearly nursed, beneath his patrician contempt, a genuine love for the hapless ''talents'' of Blaine, Mo., and thus earned the right, as an artist, to humiliate them.
He demonstrated no such love for the dog lovers of ''Best in Show,'' another improv mockumentary that certainly did kill in places, but never with kindness. With A Mighty Wind, Guest's dig at '60s-era folk music, the ''Guffman''-esque affection for flamboyant, triumphant mediocrity returns, as the ensemble simultaneously celebrates and lacerates folk in all of its faux-populist glory. Guest, Eugene Levy, and Michael McKean (who collaborated on many of the breathtakingly vacuous tunes, and who each appear as veteran folkies participating in a reunion concert) are clearly more interested in noodling around with infectious melodies and deliriously mixed metaphors than they are in nailing the genre's foibles. (The DVD extras are a trove of cut songs, with priceless lines like ''You can't fly to heaven on the wings of a gun.'')
But at the end of the day, Guest still feels at war with the very atmosphere of idiot joy he's created: His story dyspeptically insists that ''Wind'''s blinkered has-beens won't be redeemed. Whether this comes across as piquant dissonance or a sour note is largely a matter of taste, but for my money, I'd rather see these characters revel in their God-given freedom of cheese. That's pathos enough.