Chaka Khan held court for her birthday celebration at Vortex recording studio in Hollywood.
The superstar partied with a couple of hundred guests who joined Stevie in singing happy birthday -- his version, of course.
Once Stevie got behind the keyboard the party was in full swing, he and Chaka did her hit, "Tell Me Something Good", and then they battled to belt out one of his Motown classics, "Signed, Sealed, Delivered."
Joni Mitchell's another legend who came out to honor Chaka ... along with comedian Mike Epps, and later in the night Tiffany Haddish jumped on stage too.
Photo: Getty Images North America