Tangled

“Tangled,’’ which sugars, spices, and 3-Ds the tale of “Rapunzel,’’ feels even more on edge. It’s computer-generated but seems almost ashamed of how old-fashioned it is. When Rapunzel (the voice of Mandy Moore) or Rapunzel’s mother, Gothel (Donna Murphy), breaks into song, the movie insists on sight gags or a jokey lyric.

Alan Menken, the star composer who wrote “Under the Sea’’ for “The Little Mermaid’’ and “A Whole New World’’ for “Aladdin,’’ cowrote the songs in “Tangled.’’ One of them, about why Rapunzel mustn’t ever leave her tower, is called “Mother Knows Best.’’ And even as you admire how exasperatingly good Menken remains at his job (it’s been weeks and I can still hear the melodies), there’s a droop to these numbers. The movie doesn’t need them, for one thing. For another, their archness (Gothel sings with a forearm to her forehead) suggests that the filmmakers want to have it both ways — to be sincere and to sneer. The musical bits sag with uncertainty. The whole movie does.

The problem is that Disney, with Menken’s inspired assistance, mocked its animated classics a few years ago with “Enchanted,’’ a live-action farce that actually did manage to have it two ways. The movie jested, but that title turned out to be apt, too. “Tangled,’’ sadly, is also a title that makes sense. The company wants to go back to the way things were but doesn’t seem to believe it entirely can. The animators might rather be out doing “Megamind’’ or “Toy Story 3,’’ but they’re stuck with princess movies.

Their Rapunzel is enjoyably cabin-fevered. It’s been years with no computer, mobile device, or friend. (She seems, however, one Taylor Swift album away from being self-actualized.) All she really has is a pet chameleon and an undermining, overly dramatic mother, who’s always running off to Lord knows where— an educated guess would be to the nearest production of Stephen Sondheim’s “Into the Woods.’’ When a conceited bandit (Zachary Levi) hides in her tower, she gets a reluctant sidekick who’ll eventually fall in love with her.

The story’s tension — Rapunzel began life as a Grimm Brothers creation — resides in whether she’ll break free of Gothel’s “Carrie’’-like grip and discover how enchanted she is. That’s dull. All the best ideas here are visual — they’ve made Rapunzel’s 70 feet and 80 pounds of flaxen hair operate in hilarious defiance of physics. The movie has a field day with thousands of airborne lanterns, a troop of Neanderthal thugs (one is a mime), some surprisingly fleet camerawork, and good editing. I can’t think of a cartoon more confident about how to use jump cuts for comedy. Those senses of cleverness and innovation merely underscore how shopworn the rest of this movie is.

Wesley Morris can be reached at wmorris@globe.com. Follow him at www.twitter.com/wesley_morris.