For a brief, glorious moment, The Pick of Destiny looks as if it might be a full-fledged musical, which is precisely what a first-rate Tenacious D movie should be. The opening scene finds the pre-adolescent JB (played by dead ringer Troy Gentile, who also played Black's younger self in Nacho Libre) trapped in Kickapoo, Missouri, beneath the thumb of his disciplinarian dad, a crew-cutted Meat Loaf. This entire prologue, which features an additional cameo by Ronnie James Dio, is through-sung, rock-opera style—we hear the adult Black's dynamic screech issuing from his pint-sized incarnation—and it kicks Pick off with a degree of anarchic energy that the movie only sporadically recaptures thereafter. All those power chords and tremolo wails lend the goofiness a certain grandeur, just as they do in real heavy metal.
Unfortunately, most of what follows rocks considerably less hard. Fully aware that they're playing to an established fan base, the D recycle numerous bits from the HBO series and other previous efforts—at one point even performing "The History of Tenacious D," which is a tad redundant given that the movie itself chronicles their origin. The skeletal narrative, which finds the boys traveling to the "Rock and Roll History Museum" in search of a legendary guitar pick fashioned from one of Satan's teeth, builds to a climactic rock-off between the D and the Devil (Dave Grohl), a bit they've done twice before. None of which theoretically matters to those coming to the material fresh, except that the material doesn't feel fresh—it has the warmed-over, obligatory, what-you've-been-waiting-for vibe of a band's second encore.
Also—how can I put this delicately?—there's a reason why Jack Black is a movie star and Kyle Gass is not. Gass is a fine guitarist and (I presume) songwriter, but his genially dopey screen persona is as recessive as his hairline is receding; it must be intentional irony that Tenacious D begins life (in this film) as The Kyle Gass Project, since Gass tends to disappear the moment Black opens his mouth. Pick of Destiny struggles to fill the void with more star cameos: Ben Stiller turns up for one scene as a music-store guru, putting topspin on some plot exposition, and the chief villain, a scowling Russian who hobbles around on a cane, is played by Tim Robbins, who flails around desperately in search of something to play besides a limp and an accent. By the time the movie resorts to a generic low-budget car chase, the bombastic magic promised by that opening scene—"His name was young JB and he refused to step in line/A vision he did see of freaking rocking all the time/He wrote a tasty jam and oh the planets did align!"—has long since dissipated.