An uneasy mixture of raucous Will Ferrell farce and kid-friendly Disney Channel teen teleflick that never gels, “The Rocker” is notable mostly as the first starring vehicle for Rainn Wilson, so popular as Dwight on “The Office,” and the screen debut of Teddy Geiger, an up-and-coming pop singer-songwriter. But it’s not a terribly auspicious start for either.

Wilson plays Robert “Fish” Fishman, a would-be heavy metal drummer bounced from his band, Vesuvius, two decades ago—the other members of the group replaced him with a relative of the big-shot who signed them to the record deal that brought them fame and fortune. He loses his telemarketing job when he attacks a fellow-worker over Vesuvius’ upcoming induction into the Rock ’n Roll Hall of Fame and shows up at his long-suffering sister’s house looking for a place to crash. Played by Jane Lynch, she’s a mite nonplussed that he’s back (apparently not for the first time), but her husband (Jeff Garlin), who finds Fish cool, is exuberantly supportive.

As it happens, their son Matt (Josh Gad) has reason to appreciate his uncle’s return, because his band ADD has just lost its drummer just before their gig at the school prom. Though the remaining players, ultra-serious writer-singer Curtis (Geiger) and guitarist Amelia (Emma Stone), are understandably doubtful, Matt asks Fish to stand in, and the guy is suddenly seized by the old rush and acting like the wild man he’s always wanted to be. Despite concern over his fanatical intensity, the band continues to practice by webcam, and Fish’s habit of playing nude without realizing he might be seen by outsiders lands him on YouTube, where he becomes a smash, leading a snarky promoter (James Sudeikis) to sign ADD for a tour and record deal.

From here on things take the road most traveled. We’re treated to Fish’s antics on the tour, and his growing attachment to Curtis’ mom Kim (Christina Applegate), who’s accompanying the band as chaperone on its bus journey. And fatherless, deep-souled artist Curtis is both upset over his mother’s interest in the guy and tempted by the opportunities afforded by success that are stocked by their sleazy manager. The big finale comes when ADD is tapped to open for Vesuvius at their Hall of Fame bash and Fish has to come to terms with his resentment. Needless to say, his old colleagues turn out to be a bunch of arrogant, overhyped dudes who—as it turns out—can’t hold a candle to the new guys on the block.

There’s nothing awful about all this, but the script, based on a story by Ryan Jaffe, misses the opportunity for some really bold satire of the music business and is content with blandly formulaic stuff, and the direction by Peter Cattaneo (who played the nakedness card far more amusingly in “The Full Monty”) is at best workmanlike. Wilson pumps things up with the sort of manic turn in the Ferrell mode—and of course the fact that both seem not just willing but anxious to disrobe for comic effect accentuates the similarities—but there’s an palpable desperation to his turn that suggests he should tamp things down a bit. Geiger does the doe-eyed, suffering adolescent bit decently enough, but it’s the sort of Jonas brother-type performance that would really be more at home on cable. And both he and Wilson are hobbled by the utter mediocrity of the music ADD perform. It’s supposed to be good, but it isn’t—it sounds like the sort of elevator music that Fish dismisses contemptuously. Worse, the songs could have been crafted for satiric effect, but that chance is entirely missed. “Spinal Tap” this is not, a point reemphasized by the forgettable turns by Will Arnett, Fred Armisen and Bradley Cooper as Fish’s erstwhile Vesuvius colleagues.

The rest of the cast—Gad, Stone, Applegate, Lynch, Garlin—are largely wasted, and Sudeikis is all too annoying as the Machiavellian manager. Technically the picture—set initially in Cleveland but shot, as is so often the case nowadays, in Canada—is okay, but Anthony B. Richmond’s cinematography is no better than adequate, and Christopher Hargadon’s garish costumes for the rockers may be authentic, but they’re not easy on the eye.

Ultimately “The Rocker” has its moments—thanks largely to Wilson’s innate funniness—but like a mediocre CD, it’s not going to get very high on the charts.