Frankie Valli and the Four Seasons were one of the key rock groups of the early- to mid-’60s, not to mention a treasure of mid-20th century pop culture. They rose to acclaim in the Brill Building era of 1963, a year before Beatlemania struck. And like other acts of the period (such as Dion and the Belmonts and Ricky Nelson), their music evokes a simpler and gentler time — the innocence of the pre-Vietnam, Kennedy-era ’60s. There is also a tough, gritty undercurrent to much of their music that neatly offsets the effusive sentimentality of the lyrics — and that speaks to the East Coast, Italian-American origins of artists Valli, Tommy DeVito, and Nick Massi.

The idea of a musical built around the ensemble’s transition from street life to the limelight is not only a fantastic one, but welcome news given the uniqueness of the Seasons’ sound and the longevity of member Bob Gaudio’s cunningly written tunes (which still sound great, decades after they first charted). The concept excelled on-stage thanks to playwrights Marshall Brickman (co-writer of Annie Hall) and Rick Elice, and the production went on to win the 2006 Tony Award for Best Musical. But the film adaptation — brought to life by producer Graham King and director Clint Eastwood — feels laborious, ill-conceived, and woefully overlong at more than two hours.

The movie is at its best during the early scenes in New Jersey, when we watch Valli (John Lloyd Young) and his friends search for a way out of their enclave. As the characters flirt with petty crime and dazzle themselves with fantasies of a music career, the picture captures the zany, freewheeling spirit of youth. Though Eastwood’s direction is leaden, the movie does occasionally nail the ideal tone. For example, when Valli and his friends make a disastrous attempt to steal a safe that is ten times heavier than the car they want to use to transport it, the result is like a cross between a gentler version of Mean Streets, Philip Kaufman’s The Wanderers, and a Buster Keaton gag. This type of material is delightful, but unfortunately, it’s also all too brief. The picture soon descends into B-grade psychodrama, narratively structured with a series of irritating theatrical asides to the camera. The story is anchored by a battle of wills between the diminutive, put-upon Valli and Type-A aggressor DeVito (Vincent Piazza), who feels threatened and alienated by Gaudio’s genius and eventually lands the group in hot water with his irresponsible antics. Later, we watch the young men grapple with the burdens of fame, as when Valli’s constant touring carries him far away from home and threatens to destroy his first marriage and attempts at fatherhood.

None of these conflicts strain credibility per se, but they are overly familiar. We’ve seen the rise-and-fall showbiz story dozens of times before in better movies — everything from The Rose to Coal Miner’s Daughter to What’s Love Got to Do With It? — and it feels stale here. You keep looking for something fresh and interesting in the characterizations and scenarios and coming up empty-handed. It’s also telling that Valli and Gaudio (Erich Bergen) are presented as nearly spotless, whereas Massi (Michael Lomenda) and DeVito come off as neurotic and complicated; perhaps we shouldn’t be too surprised by this, given the fact that Gaudio and Valli are two of the film’s executive producers. Christopher Walken turns up as a neighborhood figure known as Angelo “Gyp” DeCarlo; he’s a welcome presence and gets to deliver a few amusing lines, but the characterization is so badly drawn that it’s difficult to determine what relationship he has with the leads.

There is another issue: The Four Seasons’ tunes, many of them bubblegummy, up-tempo, and carefree, are at odds with the pseudo-Cassavetes emotional brutality of the characters’ interactions. If Brickman and Elice (who co-wrote the screenplay) wanted to make these two extremes gel, they probably needed to carefully define the role of the music in Valli and co.’s origins — for instance, by presenting the songs as a form of deliverance from the inner-city blues, as in Alan Parker’s Fame. That sort of conceit never materializes here, and as a result, the music clashes badly with the events surrounding it. Whereas people who saw the original production on-stage often commented on the sense of joy that they carried away from it, you don’t get the same feeling from this picture. Instead, the movie makes listening to these beautiful old pop songs remarkably unpleasant; you feel they’ve been weighed down by morose and lugubrious human drama.

But all of that notwithstanding, there are several good things scattered throughout Jersey Boys — especially stellar production design by James Murakami, convincing performances by the young leads (all of them relative unknowns, which lends the picture credibility), and a single crane shot involving the legendary Brill Building that qualifies as one of the most inventive and spectacular movie moments of the year. There is also a marvelous closing-credits number, lifted directly from the stage production, in which the entire ensemble gather on a closed set and dance to the Four Seasons’ hit “December, 1963 (Oh, What a Night).” It’s a rare dose of ebullience, infectious in its joy, but also something of a mixed blessing: It has the misfortune of underscoring what we’ve been missing for the last two hours.