The veteran R&B act ran through two of their most iconic hits with the "Espresso" singer on Sunday night (Aug. 3) in Chicago.

On the final night of Lollapalooza, one of the festival's biggest headliners brought out music legends to help the crowd just "let loose and groove."

EWF wasn’t the only band to join a contemporary pop star onstage at Lolla, though. During Olivia Rodrigo’s set, she was joined by Weezer, another cross-generation collaboration that earned her the approval of the parents in the crowd who perhaps underestimated her real-life alt-rock chops.