(CNN) -- You're on a bus to Los Angeles and the cute blond girl in the third row breaks out into a rendition of "Sister Christian." You have two options: You can stare at her awkwardly or pretend you're Kelly Keagy and lend your vocals to the chorus.
It's scenes like this one, which opens Adam Shankman's new film "Rock of Ages," based on the rock opera of the same name, that have audiences split on movie musicals. Formerly a surefire moneymaker, the genre has become more accustomed to sporadic success in recent years.
Still, studios recreate such musicals, hoping for "Mamma Mia's" box office numbers and "Chicago's" critical acclaim.
Boasting names like Tom Cruise and Catherine Zeta-Jones, nostalgic rock anthems and '80s flair, "Rock of Ages" will prevail if audiences are in on the joke, said Robert Viagas, the founding editor of Playbill.com.
Director Shankman appears to agree with Viagas.
"The period sort of makes fun of itself in its own way because it was a really wonky sort of boundaryless time," Shankman, who directed, produced and choreographed the film, told The Hollywood Reporter. "I wanted to make sure the comedy and emotion were coming from the characters and not from their wigs or costumes, that they weren't always chasing the joke of the era."
Big hair and fanny packs aside, musicals have a hard enough time appealing to mainstream audiences.
"At a certain point, people lost the ability to ... imagine a realistic story being told through music and dance," Viagas said, noting theatrical underachievers like 1967's "Doctor Dolittle," 1968's "Star!" and 1969's "Hello, Dolly!"
"Movies have become so literal," he added. Some people respond better to "things that are sort of in quotes. It has to have an element of reality."
Despite Shankman's success with 2007's "Hairspray," which grossed more than $118 million domestically, he said: "I really worry about losing money for people and hurting people's careers, and ('Rock of Ages') was a really big gamble."
But the director said he was comforted by Cruise's enthusiasm and hard work as rock star Stacee Jaxx.
Cruise has said he spent about five hours a day training for the role, and it's a good thing, because Jeffrey Simonoff, a New York University Stern professor of statistics, said the "Mission: Impossible" actor's performance could potentially be a big draw.
People will be intrigued to see a star in this role who isn't usually associated with singing and dancing, said Simonoff, who co-wrote a recent study titled "Broadway Show Survival." Then there's Zeta-Jones, who won an Academy Award for her role as Velma Kelly in "Chicago."
Simonoff's research says musicals last much longer than other types of productions on Broadway. That might play into Hollywood's motivation for adapting such stories.
If a Broadway show that costs $350 for a family of four in New York can be successful, Simonoff reasoned, why wouldn't a movie version, that costs about $45 for that same family, do well?
That said, "You get less of the spectacular aspect in the movies than you do in the theater," he said. "Music is playing, dancing is going on, and you really feel it a lot more than you do on the movie screen. ... Movie musicals do get hurt by that."
On Broadway, "There's that suspension of disbelief that you go in with," Simonoff added. "You know it's on a stage. When you watch a movie, there's still some suspension of disbelief, but it feels more jarring when people suddenly burst into song."
In other words, the fact that the actors in "Rock of Ages" are constantly reacting to musical numbers could work in the film's favor.
Some people might find it odd if Sherrie, played by Julianne Hough, was sitting on a bus singing and nobody around her seemed to notice, Viagas said.
Most of the musicals that have done well at the box office of late have used a mix of dialogue and music to move a story along, much like "Rock of Ages." So it will be interesting to see how "Les Misérables," a fully sung musical, performs at the box office when it opens in December, Viagas added.
The "Rock of Ages" movie soundtrack, which debuted at No. 15 on the Billboard 200, and No. 1 on the Soundtrack chart, will likely have a better week after the film opens, said Phil Gallo, a senior correspondent at Billboard.
Soundtracks aren't huge moneymakers anymore, Gallo said. "Garden State," which earned Zach Braff the Grammy Award for best compilation soundtrack for a motion picture in 2005, was "the last, sort of, collection of music by artists that would ... greatly enhance the value of a film."
Even the "Hairspray" soundtrack debuted on the Billboard 200 at No. 20 before peaking at No. 2.
But "Rock of Ages" is driven by '80s hits like "Hit Me With Your Best Shot," "Don't Stop Believin' " and "Every Rose Has Its Thorn."
"'Rock of Ages' is filled with 11 o'clock numbers," Gallo said.
Get ready to start singing on that bus.