For Mick Jagger, having Get On Up made was a passion project.
The Rolling Stones singer got the long-stalled movie up and going after seeing the script. He produced it with Hollywood big gun Brian Grazer, who has dabbled in biopics before, such as A Beautiful Mind, and the music on Eminem's 8 Mile.
Get On Up depicts the time when the young Rolling Stones performed with Brown in 1964 - they got top billing above Brown at the T.A.M.I (Teenage Awards Music International) in Los Angeles, which enraged the legend.
Despite their past differences, Jagger and Brown remained friends for many years.
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Jagger had first witnessed Brown live at the historic Apollo Theatre in Harlem where he recorded the famed 1963 album Live at The Apollo.
"What do I recall about the T.A.M.I gig?" Jagger laughs.
"Well, remember it's 50 years ago, but it was a very exciting show and James was definitely the star. It was a pretty crazy day. He was a bit annoyed about not being last on the show," he says.
"And as I was the only one that had met him before, and I was only about 20 years old, everyone said to me that I had to talk to him about us going on after him. When you're 20 years old, you just say, 'sure'.
"People say he's the most sampled musician in the world, and he is that, but he is much more than that. We did a lot of his songs. And regardless of what music you play, if you want to be a musician, this is part of the canon. You have to know his music or you are not complete. "