Velvet-voiced soul singer Syl Johnson struggled for decades before leaving the music business in the 1980s to open a Chicago fried-fish chain. But with the dawn of hip hop came the unexpected, widespread embrace of his 1967 song “Different Strokes” – sampled by artists as diverse as Run-DMC, Michael Jackson, the Wu-Tang Clan, Beastie Boys, Kid Rock, En Vogue, Usher and Kanye West, among many others – and new opportunities for the savvy performer emerged. With a lively soundtrack and an original score by Yo La Tengo, this buoyant documentary celebrates one man who can’t stop the music. -Chris Metzler