Modestly watchable, The Rocker is nowhere near the level of Almost Famous or The School of Rock, this decade’s great movies about rock bands. However, it is the only rock-and-roll movie I can recall in which the drummer is the hero of the piece. That merits this inoffensive comedy its own niche in the lower reaches of the pantheon.

When we first see Robert Fishman (Rainn Wilson), it’s 1988, and he’s laying down a monster beat behind a hair-metal band called Vesuvius. Just as the group is about to sign with a major label, Fish is forced out by his bandmates (hammed up shamelessly by Will Arnett, Bradley Cooper, and Fred Armisen) to curry favor with the label’s president. Twenty years later, Vesuvius is a multiplatinum band selling out arenas all over the world, while Fish has moved back in with his sister (Jane Lynch) after losing yet another crappy office job. Stuck in Cleveland and drowning in bitterness, Fish is thrown a lifeline by his nephew Matt (Josh Gad), who needs an emergency replacement drummer for A.D.D., a band he has formed with two of his fellow high-school students. It starts badly – Fish can’t resist unleashing a thunderous drum solo at the prom, where A.D.D. is performing a cover of Peter Gabriel’s famously weepy “In Your Eyes” – but soon the fortysomething drummer makes himself indispensable.

Fish is really a Jack Black role, but the stranger and more intense Wilson provides a welcome change of pace, spending much of the film with long hair and wearing spangled outfits (and, at one point, no outfit at all). The star of The Office probably doesn’t have the range to become a headlining star, but all good character actors deserve at least one chance to carry a movie, and this vehicle fits Wilson fairly well. This comedy’s main problem is its tendency to go in every direction at once. After Fish inadvertently makes A.D.D. famous in a clever and internet-savvy way, he seizes the chance to party like a rock star while his teenage bandmates are too levelheaded to join him. This comic strategy might have been worth pursuing, but the movie abruptly abandons it so Fish can start dispensing words of wisdom to Matt as well as A.D.D.’s token hot-chick guitarist (Superbad’s Emma Stone) and mopey but talented frontman (Teddy Geiger, who actually does the singing on the soundtrack). There’s also a perfunctory romance between Fish and the lead singer’s overprotective mom (Christina Applegate) that comes to nothing. Director Peter Cattaneo (who did The Full Monty 11 years ago and hasn’t been much heard from since) can’t pull things together and turns the opening sequence into a slasher-movie sendup that sets the wrong tone.

BAM (300 x 250 px)

Despite the unnecessary plot lines, there’s just barely enough material to paper over the cracks here, with help from memorable supporting turns by Jeff Garlin as Fish’s straitlaced brother-in-law and Jason Sudeikis as a sleazy record-label A&R guy whose idea of a compliment is “I think John Lennon just rolled over in his grave to hide the boner you gave him!” (Um, thanks?) With much better comedies in the multiplex right now, The Rocker isn’t worth running out to see, but when you catch it on cable TV next spring, you might find yourself unexpectedly charmed.

The Rocker

Starring Rainn Wilson.

Directed by Peter Cattaneo.

Written by Maya Forbes and Wally Wolodarsky.

Rated PG-13.