"You cannot forget a Sherman brothers song for the rest of your life," says Pixar mastermind John Lasseter in an interview at the beginning of "The Boys: The Sherman Brothers Story," a new documentary about the Oscar-winning songwriting duo. That might be praise, or, given that they were responsible for such earworms as "It's a Small World" and "A Spoonful of Sugar," it might be a warning. Indeed, you just might keep on hearing their tunes in your sleep even after you finish watching "The Boys" -- or, considering its slow patches, during it.

Good-natured but overlong, "The Boys" is directed by Jeff and Gregory Sherman, sons of the songwriters, who treat their fathers with respect and their careers with reverence. From the brothers' first composition, sung by Gene Autry, through a career at Disney that had them writing songs for "Mary Poppins," "The Jungle Book" and "The Parent Trap," all the way up to a dispiriting collaboration with Kenny Loggins in 2000, Bob and Richard Sherman have had a knack for a clever lyric. But the film holds their Disney songs in such high esteem, and discusses them with such little context, that "The Boys" sometimes feels as though it is set in Disneyland, not the real world. (Indeed, it's released by Disney.)

There is no lack of great tidbits for Disney fans, from the first (awful) meeting between Disney staff members and "Poppins" author Pamela Travers to footage of the Louis Prima band playing "I Wan'na Be Like You," used as an animation reference by "Jungle Book" artists. It's touching, too, to hear that Walt Disney loved the first song the brothers wrote for "Poppins" so much that every Friday, Bob and Dick went into Walt's office and played "Feed the Birds" on the piano, even after Walt died.

"The Boys" does touch, unsatisfyingly, on the conflicts that drove the brothers personally apart even as they professionally remained a team. Longtime executive Roy Disney uses their own songs to describe them as polar opposites in temperament: "Bob is 'Feed the Birds,' Dick is 'Supercalifragilisticexpialidocious.' " But it never becomes clear why they became such bitter enemies that for decades they told their children not to speak to each other. In the end, "The Boys" doesn't do much to explain its claim that the beauty of the Sherman brothers' music came from the conflict between them, but it will make you want to pull out your DVDs of mid-century Disney classics to listen to the music.

Dan Kois is a freelance reviewer.

At Cinema Arts Fairfax. Contains mild thematic elements, smoking images and brief language.