All throughout “Beyond the Sea” I kept thinking of a line from Mike Nichols’s “Working Girl.” At one point in that 1988 comedy, the character played by Joan Cusack declares “I like to dance around in my underwear, but that don’t make me Madonna.” Kevin Spacey likes to sing Bobby Darin’s songs and wear his clothes, but that doesn’t make him Bobby Darin.

Assessing “Beyond the Sea,” in which Kevin Spacey for two hours tries to convince us that he’s Bobby Darin, is not a job for a film critic (which I’m normally not) or a music reviewer (the jury’s still out on that one), but a psychiatrist. What kind of performer would so badly want to become another performer that he would not only produce, write, and direct a film in which he plays that entertainer, but also release a CD of himself recreating Bobby Darin – and then do the same thing on a personal appearance tour? A shrink would say that he’s giving out conflicting signals – on effacing himself by hiding in another performer’s persona, but doing so in a manner so self-indulgent it would have annoyed even the egotistical Darin.

A good musical biopic communicates the essence of a persona without that performer actually being seen; at the very least you want to be able to hear their actual music. “The Jolson Story,” “The Glenn Miller Story,” and last month’s “Ray” all do this beautifully. Mr. Spacey, contrastingly, has not given us a movie about Bobby Darin, but a movie about his own apparent obsession with wanting to play-act as Bobby Darin.

In this movie, Mr. Spacey sings one Darin signature after another. He not only sings more than Darin did in any of his movies, he sings considerably more than any of the three greatest male pop singers of all time – Bing Crosby, Frank Sinatra, and Elvis Presley – did in any of their movies.

“Beyond The Sea” comes out of several traditional species of showbiz vanity project: actors who want to direct, actors who want to sing, singers who want to act, comics who want to play Hamlet. It’s also an example of a newer variety of vanity, in which contemporary performers, usually pop-rock singers, try to recreate themselves in the image of musical icons – think of Brian Setzer or David Lee Roth’s note-for-note recreations of Louis Prima or Linda Ronstadt hiring Nelson Riddle to rehash his classic charts for Frank Sinatra and Rosemary Clooney. Gary Giddins calls these “chilled classics.”

What’s really disappointing is that both Darin’s personal and professional lives contain enough dramatic plot pegs for not just a movie but a long-running dramatic series. A sickly child, he was told by doctors that he wouldn’t live to see 15.An underdog from the Bronx, he wrote and sang a string of jukebox hits that made him, for a hot minute, the biggest new star in pop music. Even at the height of his fame as a rock star, though, Darin was ambitious to prove himself in the more challenging world of grown-up pop music.

He also did well as a movie actor, winning an Academy Award nomination and, in one role, the hand of the girl of his dreams, actress Sandra Dee (Kate Bosworth in the movie). He dabbled in country and folk music, and like many in the post-Kennedy era, spent a lot of time trying to “find” himself. The most dramatic scene in Darin’s life occurred when the woman he had been raised to believe was his sister told him that she was actually his mother.

Strangely, instead of giving us a straightforward narrative sequence of Darin’s life story, the filmmakers have come up with an elaborate, awkward structure, which begins with Spacey-as-Darin purporting to be making a movie about his own life. He meets the child actor (William Ullrich) playing himself as a boy (in the biopic within a biopic) and most of the narrative is framed as a dialogue between the young Darin and the mature Darin.

With this framework, similar to “De-Lovely” or “Chaplin,” “Beyond the Sea” is obviously trying to avoid the traditional drawbacks of the genre – such as the flashbacks in “Ray,” which were the hokiest part of the project. Screenwriters Lewis Colick and Kevin Spacey have tried to approach the material with Darin-like irreverence – as when someone tells Spacey-as-Darin that he’s too old to play himself. Yet their eagerness to escape cliches simply reinforces them. Instead of capturing Darin’s energy and charisma, they translate his diverse, multi-faceted career into cinematic schizophrenia.

The most egregious error made by Mr. Spacey, in his role as producer, was the decision to have Mr. Spacey the actor do his own singing (the least they could have done was give us the actual voice of the film’s subject, the way “Ray” so generously does). It’s not that Mr. Spacey can’t sing or has a bad voice. Darin actually had less chops and technique than his fellow Italian-American pop star, and Mr. Spacey has only slightly less vocal ability than his subject. But Darin’s singing is distinctive, beyond recreation. Mr. Spacey’s vocals, with their slavish mimicking of Darin’s wise-cracking ad-libs and scat interjections, only serve as evidence that Darin was, literally, inimitable.

“Beyond the Sea” is most successful when it realizes that there’s nothing wrong with sentiment presented with honesty. Mr. Spacey is more convincing as the comparatively older Darin, and his strongest performance is “The Curtain Falls” (at 27, Darin was already singing his equivalent of “My Way”). Had the movie ended with Mr. Spacey singing this song, it would have been a predictable but moving ending. But the script denies us even that – cue the dream child, a ludicrous watch metaphor about running out of time. Writer-director-star Mr. Spacey simply refuses to leave the stage.