And the film's subject -- the Empress of the Blues herself, Bessie Smith -- was as big a persona during her day as the production was in scale. Latifah plays Smith in the HBO biopic, which takes a closer look at a star who rose to prominence in the '20s and '30s.
It was a film two decades in the making for Latifah. And Greenberg, who plays record producer John Hammond, admits that it was pretty enthralling to watch her bring it all to fruition. "She's unbelievable. She's been working on this movie for 22 years, trying to get it made, so just to see her dreams come true right before your eyes was amazing," he says.
"And I don't know anybody else who could play this role," he adds. "I mean she was perfect for it and she sang all the stuff. She's really a really amazing woman, like super laid-back with everything she had going on. I don't know how she does it all. She was great to work with and a lot of fun and very welcoming."
The pair had to translate that respect off-screen into what would be a mutual professional love for one another onscreen. Hammond, who also worked with Billie Holiday, Bob Dylan and Bruce Springsteen, among others, helped to cultivate Smith's talents and make them accessible for a larger audience. And together Greenberg and Latifah discussed his role in Smith's career while filming the Dee Rees-directed biopic.
"You can just tell her passion. She was in the zone. We didn't really talk much about what inspired her to do it or why she was doing it we just kind of ... we just hung out," he recalls of making the film. "It was very comfortable with her. The only thing we ever really talked about was John Hammond and how he was like 'full of crap,' she would say, 'but the good crap.' I like that."
While Latifah shouldered most of the burden of having to bring a larger-than-life persona to life, Greenberg also wanted to make sure he had the details of playing Hammond down. The musician, who will release his next album, Everything Changes, on May 26 shared he was familiar with the legendary producer but did deeper research.
"I didn't want to screw it up, so I found some video footage of him on YouTube and I recorded his voice and I would constantly listen to his voice," he says. "I tried to get his cadence down and I think I got it. Some people said they knew him and I did a pretty good job and I'll take that. You want to be true to the character."
And while Hammond's chapter in Smith's life is only briefly explored in the movie, Greenberg says "I don't have a huge role in it it, but I think it's pivotal in the movie and in her life. He introduced her music to the mainstream, which she never had before and he was really the only white guy she ever trusted. And I met Bessie Smith's granddaughter at the premiere and she told me that. And I thought that was really cool. And they had a real love for each other."
The film is a pretty in-depth examination of the singer's life before she died in a car accident at 43 in 1937, with a focus not only on her professional relations but also romantic ones.
"She doesn't apologize for who she is and she was a rock star, " he says. "She had a girlfriend while she had a boyfriend while she had a husband at the same time. She didn't apologize about it and I feel like that's a very modern-- well, maybe even that's even a little too extreme for modern day-- but with her sexuality, I feel like, at that time, was pretty unheard of for someone to be that comfortable with themselves. And now it's, thankfully, it's very common. What I think was so amazing about her was she lived her life without apologies."
"She was like a Janis Joplin," he adds. "She was a rock star. She was hard drinking and she liked to fight. She was great."
The film also stars Mo'Nique, Michael Kenneth Williams, Khandi Alexander, Tory Kittles, Mike Epps, Oliver Platt and Charles S. Dutton. Bessie premieres on May 16 on HBO at 8pm ET.