Joni Mitchell sings at star-studded Gershwin Prize concert

On Wednesday night, the Big Yellow Taxi singer was presented with the U.S. Library of Congress' Gershwin Prize for Popular Song at an event staged in Washington, D.C. After accepting the prestigious honour, Joni thanked her friends and peers for attending: "So many people I care about are here tonight. New friends, old friends. It's kind of thrilling." Joni Mitchell's speech / according to USA Today. At the end of the evening, Joni also stunned the audience with a rendition of George Gershwin's Summertime...