Watch President Obama Go 'On the Road Again' With Willie Nelson

President joins country legend in a sing-along for special PBS show saluting the troops

"Harlan Howard proclaimed country music 'three chords and the truth.' Garth Brooks said it's 'honesty, sincerity and real life to the hilt.' And Dierks Bentley called it 'the best shrink that 15 bucks can buy,'" said President Obama at a 2009 White House concert.

Fast forward five years, and the Commander in Chief isn't just quoting country music, he's singing it.

The president and first lady Michelle Obama hosted several hundred American service men and women, veterans and their families last week for a special salute to the troops, filmed for the PBS series, In Performance at the White House. The eclectic lineup of artists paying their musical respects included country icon Willie Nelson, queen of R&B Mary J. Blige, rock legend John Fogerty, rapper Common and Latin pop star Romeo Santos, who all performed live on the south lawn of the White House. Alt-rockers Daughtry were brought in live via satellite from their USO concert in Japan. President Obama noted that the mix of genres was fitting, "because here in America, no matter where you're from, no matter what music you listen to, we're all united in our respect and admiration for our brave men and women who wear our country's uniform."

All of the artists, along with Mr. and Mrs. Obama, joined Nelson's encore performance of his classic "On the Road Again." The country legend summoned the president to sing along, and Obama proved he knew the words… at least the chorus. (Watch above.)