A successful production of "Rock of Ages" requires a delicate balance. It's not so different from the traditional musical -- except in its music. The characters who burst into song on the bus, at the bar and even at the urinal, are not singing showtunes, but hair metal rock from the 1980s.

Surprisingly, the man who's turned the musical into a film was just the guy for the job. I say "surprisingly" because Adam Shankman isn't known as a dude who likes to rock. The 47-year-old practically grew up on the Sunset Strip, which is where "Rock of Ages" is set, circa 1987.

"I am '80s rock," says Shankman, best known for directing 2007's "Hairspray," with some emphasis at a roundtable with in Los Angeles a few weeks ago. He can remember his first concert: The Cramps at the Roxy. "The lead singer did things I'm still afraid to do. To myself," he jokes.

Shankman cast actor-singers of varied backgrounds, who all had to tease their hair, put on some spandex, and belt out such "classics" as "Pour Some Sugar on Me" and "Here I Go Again."

Julianne Hough wasn't even born when some of those songs were released. But the 23-year-old found that timing wasn't her real challenge. "I didn't even know I sang a certain way. But apparently I sing country," she says with a laugh, talking about how she had to get rid of that twang before filming.

Hough shares a good deal of chemistry with her co-star Diego Boneta.

Boneta had to do some vocal work, too: The Mexican-born singer-actor could certainly pass for American in conversation. His accent is almost gone. The music, on the other hand, was no problem.

"Growing up, that's all my parents listened to," he says. "When I was 8 years old, I was listening to U2, the Police and Queen. Even before auditioning for the part, I knew these songs."

Malin Akerman, the lucky actress who plays Tom Cruise's love interest in the film, has been dying to do a musical for years. She was even in a rock band about a decade ago. But she'd never gotten a singing role before.

"There's a reason we never got picked up by a record label," she says of the band. She blames her singing.

Justin Theroux is an actor -- best known these days for dating Jennifer Aniston -- but he was strictly behind the scenes in "Rock of Ages." He wrote the film (though he dresses like anything but the typical Hollywood screenwriter, in a skinny tie and jeans.)

To be fair, he did actually act out parts of the film -- in private.

As an actor, he says, "I'm really sensitive to writing terrible dialogue for someone." So when he's working on a script, he half-performs, half-writes. It's the best way, he says, not to "saddle someone with ridiculous amounts of exposition."

Kelly Jane Torrance is The Washington Examiner movie critic. Her reviews appear weekly, and she can be reached at ktorrance@washingtonexaminer.com.