If Hollywood blockbusters are currently crippled by fear of the unknown, Broadway musicals – an ever-increasing number of them based on Hollywood blockbusters – are hardly less guilty. The jukebox musical is, if you will, the Great White Way's superhero reboot: their safest gambit, removing the greatest variable in a genre that has, after all, always been reliant on existing story material. Who needs composers when perfectly good popular discographies are there for the taking? “Jersey Boys” was a swift hit when it opened on Broadway in 2005; credit zesty staging or a tidily structured book if you will, but it's a show that owes its pull to one of the most buoyant American songbooks in Top 40 history.

Those creamy harmonies, those tightly syncopated choruses, that unearthly falsetto: Frankie Valli and the Four Seasons hadn't the artistic reach of contemporaries like The Beatles, nor the cool strut of the Detroit acts to which they were routinely likened as pale pretenders. What they had were infectious, indestructible tunes, and a lot of them – enough to sustain and animate an otherwise familiar showbiz story on stage 40-odd years later. The rise-and-fall-and-sort-of-rise narrative of the Seasons, its requisite personal rivalries tarted up with Mob intervention, is hardly as remarkable as the brash sonic blast of their radio hits.

Funny, then, that pop is the furthest thing from the mind of Clint Eastwood's “Jersey Boys,” a strained, solemn screen transfer that digs behind the music – in VH1 parlance – and discovers very little indeed. It's an adaptation at once heedless and cowardly. Anyone who thought that the director wouldn't be able to fashion a Clint Eastwood film out of the Four Seasons' story is proven ever so wrong; anyone who thought the director couldn't film a musical, on the other hand, is presented with little evidence to the contrary. He barely makes the case himself: what's most immediately unexpected and retrospectively unsurprising about Eastwood's “Jersey Boys” is that it's not really a musical at all.

In the missing genre's stead are multiple fragments of others: here a Scorsese-style community frieze in the “GoodFellas” vein, complete with Joe Pesci connection, there a soft-lit but dirt-streaked bio-melodrama along the lines of “Ray” or “Walk the Line.” The bleak-bitter nostalgia of David Chase's New Jersey surfaces in some scenes; in only a few others, the garrulous kitsch of David O. Russell's East Coast studies in loserdom. All are approaches suggested by the script (by the show's book writers Marshall Brickman and Rick Elice) but not actively pursued by Eastwood's direction, which applies the same stately rhythm and chocolate-charcoal finish to the band's heady ascent and protracted disintegration. No one could accuse Eastwood of having stars in his eyes, but I'm not sure any rock-era biopic has less vividly conveyed the narcotic rush of celebrity.

Following a teasing, overture-style jangle of the immortal “Oh What a Night!” keyboard line over the opening credits, “Jersey Boys” makes its audience wait a good half-hour before giving them a complete song at all. Much time is spent on the band's rough-and-tumble roots, with the teenage Valli (then named Francis Castelluccio, played by the role's Tony-winning originator John Lloyd Young) introduced as a shy barber's apprentice. He's equally in thrall to local Mafia don DeCarlo (Christopher Walken, as Walkenesque as you please) and young crook Tommy De Vito (Vincent Piazza), a jobbing band frontman who picks up on Valli's dulcet tones; when De Vito's sent to prison, he enlists Valli as a replacement singer and the future Four Seasons are born.

Joining them and dim-bulb bassist Nick Massi is Bob Gaudio (Erich Bergen), a clean-cut songwriter with one novelty hit to his name. Gaudio is water to De Vito's oil slick, but Valli insists on his recruitment. De Vito's hostile skepticism is unwavering even after Gaudio's handsome presence secures them the interest of hitmaker and lyricist Bob Crewe (the wonderful Mike Doyle); when Gaudio presents them them with the bones of “Sherry,” the Seasons' eventual #1 debut, their ensuing success never papers over the group's personal differences.

It's at this point that one expects the film to blossom into full musical color, even as the signature desaturation of Tom Stern's cinematography remains non-negotiable. Yet despite three near-successive numbers – as prosaically filmed as if Stern's camera were part of the “American Bandstand” crew – Eastwood remains stubbornly uninterested in the sensation, emotion or even the mechanics of performance; the songs themselves (“Walk Like a Man” and “Big Girls Don't Cry” among them, dutifully recreated with Young's astonishing approximation of Valli's rubber-ball vocals) are textually immaterial.

After this brief run, the film reverts to presenting songs in stunted, heart-leaping snatches, as the band's unresolved tensions and plunging financial crises talkily take center stage. Late in the game, the film summons some snap for a vigorous full-length performance of Valli's brassy 1967 comeback single “Can't Take My Eyes Off You”; for three pulsating minutes, the story is told through the music, and not over it.

Brickman and Elice's script retains the stage show's four-part structural conceit, whereby the action is narrated relay-style by different band members at different stages (or seasons) in their career. It's an elegant device for a stylized musical, but barely a sustainable one for the naturalistic backstage drama that Eastwood has at least half an eye on making; without the songs as bridging devices, the limitations of the band's narrative arc come to the fore. Despite sporadic segues into fourth-wall-breaking delivery with which Eastwood seems acutely uncomfortable, the boys' individual voices get lost in the back and forth, appealingly delivered as they are by a puppyish quartet of actors; other characters (notably Valli's dismayingly shrewish wife and ill-fated but undefined daughter) hardly register.

Eastwood is rarely a careless director, even when his handling on the material is this badly fumbled, but even his typically astute command of period and place feels off here. “Jersey Boys” conjures no sense of public feeling, political movement or pop-cultural zeitgeist outside the Seasons' airless bubble; for all the dedicated work of his design team, Eastwood's rigid palette and chamber-film ambience thwarts any sense of chronology in a lengthy 130 minutes. (“That's a nice color on you,” Valli says at one point to a knockout in a gray dress – as if she had any choice in this story world.) None of which would be fatal if Eastwood's ears were just a little more open. “When everything dropped away and all there was was the music,” Valli observes at the film's close, “That was the best.” If only this conscientious but joyless film felt the same way.