Chadwick Boseman, center, plays that funky musician. (Universal Pictures)

For last year’s “42,” Chadwick Boseman had to learn to play baseball like Jackie Robinson. For “Get On Up,” out Friday, he had to learn to perform like James Brown. Which made professional baseball look easy.

“I had to get up every morning and lace ’em up, no matter what kind of shoes they were,” Boseman says of his two biggest roles. “Here’s the key difference: When you’re performing onstage and you’re entertaining people, you have to look like you’re enjoying it. When you’re playing a sport you can look tired, you can use the pain — but you can’t really use it when you’re onstage.”

“Get On Up,” which charts Brown’s rise to fame, is no hagiography, addressing his childhood in the Jim Crow South, his drug addiction and his brushes with the law. 

“I think James Brown is a hero — a reluctant hero — but I also think he’s an antihero,” Boseman says. “You don’t get to see African-American characters like that a lot. It’s refreshing to see someone that you love anyway, regardless of the bad stuff they’ve done.”

The film’s best scenes are the musical performances, when Boseman isn’t so much acting as channeling the Godfather of Soul. Director Tate Taylor (“The Help”) slyly reveals a difference between the shows Brown plays for mostly white audiences and those for mostly African-American crowds. The difference, Boseman says, isn’t in Brown’s performance but in the reception.

“Like at the Apollo [Theater] — the Apollo was his home — the audience knows the culture better. They understand how to respond.” Contrast that with a scene in which Brown performs on a TV Christmas special, surrounded by cheerful white folks in ski sweaters politely swaying and clapping on the beat. Reactions aside, Brown managed to achieve huge crossover success. 

“He may have been singing these funk songs to audiences that weren’t African-American,” Boseman says. “But they still got it. They got it.”

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