90% smart, 10% silly

The several hundred extras are supposed to look as if they are enjoying a pretty good concert, but they don’t really have to act: The music is that good. John C. Reilly is on the stage of downtown’s Variety Arts Theater and he and his 1950s-era band are belting out a Roy Orbison-style love ballad called “A Life Without You.”

Dewey Cox, the charismatic singer Reilly plays in the film, has dedicated the song to his wife, and the lyrics and performance are emotionally convincing.

Darlin’, you must believe

I could never leave

you if I tried

A life without you

is no life at all

As the song builds to its rousing climax, director Jake Kasdan’s cameras sweep over the audience. The extras roar and Cox basks in the adulation. It feels exactly like a big, emotional highlight out of “Walk the Line” or any other modern musical biography -- “Ray,” “La Bamba,” take your pick.

And that, for a minute, is the point.

When Cox’s romantic ballad is edited together by Kasdan several months later, the singer’s harmonious declarations of fidelity will run smack against a hotel orgy with Cox and an explicitly naked roadie at its center.

The most perceptive and authentic satire is just 10% different from the real thing, and that’s the narrow target Kasdan and Reilly’s “Walk Hard: The Dewey Cox Story” is aiming for. While movie spoofs are as common these days as comic-book sequels, there’s a marked distinction between “Walk Hard,” which opens Dec. 21, and such broad parodies as “Epic Movie,” “The Comebacks” and “Scary Movie.”

While all spoof films naturally try to have fun and make moviegoers laugh, “Walk Hard” wants to be silly by being smart.

As constructed, “Walk Hard” is consciously self-important; it’s as if its makers believe their movie is significant. “We are trying as hard as we can to make it look like a real American biopic,” Kasdan says as Reilly prepares to run through “A Life Without You” one more time. “We will always say whenever we’re stuck, ‘What would they do in a real movie?’ ”

The movie has plenty of gross-out gags and visual pranks, but “Walk Hard” also is designed to send up subtle biographical filmmaking tropes, including incalculable narrative montages, repeated visits to rehab and having the lead actor play the central character over a preposterously long time span (Reilly starts playing Cox when the singer is just 14 years old).

When, as a child, Dewey and his older brother Nate go out and play, his brother remarks, “Ain’t nothing horrible gonna happen today!” As is all but certain in the musical biography, that kind of pronouncement can only foretell some terrible tragedy is just a few frames away. In the case of “Walk Hard,” Dewey accidentally slices Nate clean in half with a machete. (Leaving Nate and Dewey to calmly discuss what’s happened.)

“Jake called me up and said, ‘Let’s do a movie that’s going to make fun of all of these biopics,’ ” says producer Judd Apatow (“Superbad,” “Knocked Up,” “40-Year-Old Virgin”), who worked with Kasdan on the television series “Freaks and Geeks” and “Undeclared” and the Kasdan-directed movie “The TV Set.”

“So we sat down and watched all the movies,” Apatow says, “and then, late every night, we talked about them, giggling about all the devices we noticed.

“Every scene has to be a pivotal turning point -- it’s the only way you can compress an entire life into a two-hour movie,” says Apatow, who shares the “Walk Hard” screenplay credit with Kasdan. “So anyone who walks in the door is vital. And that becomes, very quickly, ridiculous.”

What isn’t ridiculous are some of the steps Kasdan took to make “Walk Hard” look and feel like the very thing they were lampooning. Before production began on the film, Reilly recorded more than 40 original songs, with the “Walk Hard” theme written by songwriter Marshall Crenshaw.

Because the movie has wall-to-wall music, Cox has to sound good enough that you’d buy him as a music legend. Furthermore, his music has to progress through half a century of styles. And yet, most of the songs are a bit off lyrically; as with “Life Without You,” they are simply lies; in “Let’s Duet,” they are overstuffed with raunchy double-entendres. In his professional debut in an all-black nightclub, Cox performs a bluesy number called “Mama, You Gots to Love Your Negro Man.”

At the same time, there are more than a few “Airplane!”-style teases. Having noticed that record-label executives in other music biographies are clearly Semitic, Kasdan takes the stereotype one step further: His executives -- L’chaim, Mazeltov and Schmendrick -- are Hassidic Jews who occasionally speak Yiddish.

As the call sheet for the film puts it, “The story of Dewey Cox is both a comedy and a tragedy. Please act accordingly.”

First cut is the deepest

With the film nearly finished on this March day, Kasdan is in a Sony mixing stage, working with his editors to polish the film’s sound levels, musical cues and effects. “This is the last chance,” the 32-year-old Kasdan says, “to make it significantly better.”

The film’s first big comic set piece, falling just a few minutes into the film, is Dewey’s slicing his brother in two (a neat cut at the waistline). Kasdan’s sound team has added some effects that sound straight out of “Saw,” and since they are heard before the severed body is seen, they’re telegraphing what the audience sees next.

“I think we might have gone a little overboard,” Kasdan says. “It sounded like a horror movie -- not funny. Let’s just take the slicing sound down 20%.”

Kasdan has struggled to find the right comic balance in the orgy scene too. As originally scripted, Dewey’s sexual shenanigans were intercut with “A Life Without You.” One moment he was proclaiming his love for his wife, the next he was graphically repudiating it. Now the sex scene follows the song. Kasdan and his team also have wrestled with how long the cameras should linger on the roadie’s exposed penis; for now, it’s there for a few seconds, but it had been a longer shot.

“It’s a fine line with that kind of stuff,” Kasdan says. “One of the things we have been trying to suss out is how much sex we can show. How much raunchiness seems like fun, and how much makes people feel uncomfortable? If you’re alienating people, it’s not something you want in a movie.”

One thing research screenings have shown is great affection for Cox’s music. The film’s release will be accompanied by a soundtrack album of a dozen or so songs, and possibly a larger boxed set. “A box of Cox,” says Reilly, who has sung in several other movies, including “A Prairie Home Companion.” There might even be a live Dewey Cox musical tour in key cities, which is somewhat complicated by the fact that Cox is no longer alive at the movie’s conclusion. “Maybe it will be a tribute show,” Reilly says. “We haven’t yet figured out the meta joke yet.”

Reilly says “Walk Hard” shouldn’t be seen as an indictment of Hollywood’s obsession with the genre, even as he notes nearly a dozen musical biographies are in development.

“I actually love ‘Walk the Line’ and ‘Ray,’ ” the actor says. “And you won’t find a bigger fan of Johnny Cash or Roy Orbison or Ray Charles than me. So we are not poking fun at these musicians. We are razzing the people who made these movies. I guess we’re just looking at the larger question of how we make people look mythic.”

“Walk Hard,” Reilly admits, “is very broad at times. But if you’re going to stay with a movie, you have to care about something at some point -- the characters, or the story. A lot of people have come up to me and said, ‘I kinda got choked up at the end.’ ”

Dewey Cox would have wanted it that way.

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john.horn@latimes.com