In a performance for the ages, David Crosby and Graham Nash joined Jimmy Fallon (dressed as Neil Young) on Wednesday night's episode of the funnyman's 'Late Night' talk show for a rendition of teen pop star Miley Cyrus' 'Party in the U.S.A.'

The performance started with the show's announcer introducing the crowd to Neil Young. Fallon, dressed as Young, sat on a stool with a guitar and delivered a spot-on impersonation of Young as he began singing an earnest rendition of Miley's perky hit single.

Shortly thereafter, Crosby and Nash appeared onstage to back up Fallon on such compelling lines as "And a Jay-Z song was on" and "Noddin' my head like yeah." The folk-rock duo stuck around for the remainder of the song, providing vocals on the tune's chorus.

Crosby seemed a little embarrassed to be taking part in the comedy bit, but Nash appeared to be totally into the performance. It's not the first time Fallon has appeared as Young on the show. He's sung a number of pop songs dressed as the folk-rock legend, including a duet with Bruce Springsteen on Willow Smith's 'Whip My Hair.'

Later on in the program, Crosby and Nash performed their song 'Don't Dig Here' in tribute to the earthquake victims in Japan. The duo also played the tune "Just a Song Before I Go' as a web-only exclusive.

Watch David Crosby, Graham Nash and Jimmy Fallon Perform 'Party in the U.S.A.'

Watch Crosby-Nash Perform 'Don't Dig Here'

Watch Crosby-Nash Perform 'Just a Song Before I Go'