Reggae artist Matisyahu joins Moby, Natasha Bedingfield, Cold War Kids, Imogen Heap, Talib Kweli and others for the new documentary, 'Call + Response.' The film, directed by Justin Dillon, focuses on the unsettling truth that there are more than 27 million people enslaved in the world today. A combination of celebrity interviews and artist performances, the "rockumentary" features Matisyahu covering a classic song from his idol, Bob Marley.

"When I was around 14 years old, someone introduced me to Bob Marley," Matisyahu said at his 2006 Sessions. "That's what really turned me on to reggae music. For the first two or three years, I didn't know that there was another band or performer besides Bob Marley. Listening to those lyrics and songs had a big influence on me, and I just connected to it. His music was universal."