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The long-awaited release of CSNY 1974, a box set documenting the band's 1974 tour is set for Tuesday. To celebrate, Crosby, Stills and Nash will perform on NBC's The Tonight Show Starring Jimmy Fallon on Monday without Neil Young -- or will they?

In 2011 when David Crosby and Graham Nash made an appearance on NBC's Late Night with Jimmy Fallon, they sort of reunited with "Neil Young." Fallon does a spot-on impersonation of Young, and Crosby and Nash sang background vocals as Fallon, dressed as Young, did a version of the Miley Cyrus song, "Party in the U.S.A." Afterwards Crosby told us Fallon "does Neil brilliantly... I had a very tough time trying to keep a straight face."