The new film “Idlewild,” starring the hip-hop duo OutKast, is an ambitious attempt to resuscitate the musical, but it ends up making a case for why music videos should be kept to five minutes or less.

The ambitions of Andre “3000” Benjamin and Antwan “Big Boi” Patton have always been set high; the question is only how far they’ll get toward reaching them.

At their best, the duo has transcended their own formats, mixing genres and their own styles to create something distinctive. Musically, the group broke boundaries with both 1998’s “Aquemini” and 2000’s “Stankonia.” And 2003’s joint album “Speakerboxx/The Love Below” won the Grammy for Album of the Year.

But that album, which consisted of two solo discs packaged together, also fueled persistent breakup rumors. Each member’s distinctive style is evolved enough to produce solid solo work, and aside from their common background and interest in creating quality music, there doesn’t seem much to keep the two performers together a lot longer. At its best, their work transforms competing elements into new and unexpected sounds.But at times, the opposing styles just quarrel.

And this is the problem with “Idlewild,” which starts off promisingly enough. Set in 1930s Georgia, the film stars Messrs. Benjamin and Patton as friends from different sides of the tracks who have little in common besides their shared affection for each other and music. Mr. Benjamin plays Percival, a mortician’s son who grows into a sad-eyed piano player. Mr. Patton is Rooster, a petty crook with an unusual but useful pairing of skills at both rapping and math.

The two friends grow up in the small town of Idlewild. It seems they do most of their growing up at Church, a scandalous speakeasy filled with loose women, fast money, and strong liquor. As adults, Rooster struggles to juggle his career (and sexual) aspirations with his family life, while Percival must decide between living the life he wants or the one his father has laid out for him.

While the characters deal with their very traditional problems, their surroundings are imbued with the beautiful, whimsical, and rich elements of fantasy. Director Bryan Barber has created a parallel universe of the 1930s jazz world, flecked with popular elements from the 1940s, 1950s, and today.

Certain images jump up, leaping from their setting in the way that elements of music videos demand attention.The aesthetics of “Idlewild” are turned up to 11, with the scenery, design, and music all demanding screen time, at times adding to the mystique of the script and at others stealing from it.

This is matched by the talent onscreen.Dance numbers, solos, and characters are created to convey an aura of decadent gangster life. Celebrity cameos abound — Ving Rhames makes a great impression with his minimal screen time, and the casting of R&B siren Macy Gray as a drunk lounge singer seems especially inspired.

But as the plot moves on, what was bouncy and exhilarating becomes domineering and overdone. The cartoonish animation that could promise some sort of overriding whimsy during the opening credits turns out to be meaningless sleight of hand.

The plot is mostly staid, as both Rooster and Percival toy with the parallel joys and pitfalls that plague thug life today. But as the film progresses, the plot points seem more and more a backdrop for the music that OutKast has created for the film.

The second half of the film especially starts to feel like an extended music video. The songs don’t always coincide with what is happening in the plot, and often it seems as though the action gets rushed along in efforts to make it to the bridge.

Mr. Barber, a veteran music video director, has a clear aesthetic for each character, dance sequence, and song. But while each of the song segments would make an exquisite video, the transition between the action and musical interludes gradually becomes more stilted, the foreshadowing more irritating, and some of the funereal scenes more creepy.

And the acting cannot surpass the flaws in the plot. Mr. Benjamin has stated that he is interested in taking some time to pursue his acting career, and has appeared in films such as “Four Brothers” and “Be Cool.” But it is Mr. Patton who looks far more at ease on the big screen. Both characters utilize the known assets of the two rap stars, with Mr. Patton’s Rooster a trickster charmer with an aptitude for rap and Mr. Benjamin’s Percival a shy but slyly dressed mortician with an aptitude at the piano. But the incessant assumption that Percival doesn’t recognize his own talent becomes tired quickly, as does Ms. Benjamin’s doe eyed, sheepish stare.

But though “Idlewild” does not quite achieve everything it sets out to do, it does make interesting strides. The film’s attempts to update the 1930s aesthetic with the best of today make a compelling case for a more contemporary return to musical cinematography. It doesn’t quite all come together, but the effort is worthwhile nonetheless.

“Idlewild” is certainly not the best product that OutKast has tried to sell. But like many of their less outstanding attempts, it is not a failure as a thing itself, but because these two men are clearly capable of greater achievements. “Idlewild” may not be remembered as their best work, but they ought to surpass it soon, either together or apart.