Charles McQuillan/Getty Images(CNN) - With hundreds of songs under their collective belt, The Rolling Stones have plenty to choose from when it comes to performances.
But they weren't afraid to take things back to their roots Wednesday night, when their No Filter tour stopped near Washington, delighting the audience with a song they haven't played for nearly 50 years: Don Covay and the Goodtimers' "Mercy, Mercy."
"It's a long time ago, so we're going to try to remember it," frontman Mick Jagger, 75, said before diving in.
The last time the Rolling Stones played the song was July 5, 1969, at a free concert in Hyde Park in London just days after the death of guitarist Brian Jones.
The English rockers postponed some tour dates after Jagger had a heart valve replacement this year, but No Filter picked up again in June.