Tina Turner, Corinne Bailey Rae and Leonard Cohen are among the stars who'll join jazz great Herbie Hancock on his upcoming Joni Mitchell tribute album. Hancock has reworked a handful of Mitchell classics on River: The Joni Letters, and he's asked his famous friends to join him in the studio. Mitchell herself joins Hancock for one track, The Tea Leaf Prophecy, while semi-retired Turner sings on Edith + The Kingpin. Other singers featured include Norah Jones and Luciana Souza.