STEVIE Wonder and Chaka Khan had the crowd partying like it was 1999 all over again at a tribute concert to the late music superstar Prince.
Khan brought Wonder on stage in front of 17,000 fans at the Xcel Energy Center in St Paul, Minnesota, to duet on Prince's I Feel for You, a 1984 hit for Khan.
Wonder got the sold-out audience cheering with his signature harmonica riffs, and the pair then performed 1999, with the crowd clapping and dancing along.
Friends and former bandmates of Prince celebrated the Oscar and seven-time Grammy winner, who died of an accidental painkiller overdose in April at his Paisley Park recording complex.
Before the concert, St Paul mayor Chris Coleman read a proclamation on the outdoor plaza declaring Thursday Prince Day in Minnesota's capital.
Singer Christina Aguilera had cancelled her scheduled appearance as she fights a "vocal illness", and was replaced by British singer Jessie J.
Aguilera said in a statement: "It is with a heavy heart that I cannot perform this evening and join the amazing talent on stage to pay tribute to the legend that was Prince. He will remain in our hearts and inspire our music until the end of time."
John Mayer also bowed out of the concert earlier, citing a "change of schedule".
Prince's sister said she hopes the concert will bring closure to Prince's grieving fans, describing the show as a public memorial to the star.
