Our pool of genuinely funny music performers has never been large. Musicians get timid about humor, with reason. Audiences take earnest artists seriously and let time and taste catch up to anyone who takes their own importance with a grain of salt.

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."

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