Flashback: Bob Dylan and Paul Simon Duet on 'The Sound of Silence'

The moving performance was a nightly highlight of their 1999 co-headlining tour

Shortly before Bob Dylan and Paul Simon went on the road together in the summer of 1999, the two of them got together at Paul Simon's New York apartment with a couple of acoustic guitars and began sketching out ideas for possible onstage collaborations. "We were singing folk songs," Simon said. "Some were obscure, some were better known. It was just two acoustic guitars and it sounded great. But as we got closer to the show, it became apparent what people wanted to hear was us singing each other's songs. So that's what we did."

The tour began at the World Arena in Colorado Springs, Colorado, on June 6th, 1999. Simon played first that night (they switched off each night), and after his set Dylan came out for duets on "The Sound of Silence," a medley of "I Walk The Line" and "Blue Moon of Kentucky," and "Forever Young." By the second show they had swapped out "Forever Young" for "Knockin' On Heavens Door"; they stuck with that set list for the rest of the tour, though some nights the throwback medley consisted of "That'll Be The Day" and "The Wanderer." Here's video of them performing "The Sound of Silence" in Portland, Oregon, on June 12th, 1999.

Simon and Garfunkel covered Bob Dylan's "The Times They Are-A Changin'" on their 1964 debut LP, Wednesday Morning, 3 A.M. Five years later, Bob Dylan returned the favor when he covered "The Boxer" on Self Portrait. But their paths rarely crossed until they hit the road together in 1999. "I consider him one of the preeminent songwriters of our time," Dylan told USA Today shortly before the tour began. "Every song he does has got a vitality you don't find everywhere."