The song "Get Together" by The Youngbloods was also used in the Season One episode Volunteers, which was also set in 1969. It is the only case of an end song being reused in a later episode as a flashback song.
Soundtrack includes many of the performers actually at Woodstock. This episodes features "Darling Be Home Soon" by Joe Cocker, "Singing in the Air" by Thunderclap Newman, "Colours" by Donovan, "Piece of my Heart" by Big Brother and the Holding Company (Janice Joplin), "Get Together" by the Youngbloods (Jesse Colin Young), and "The Weight" by The Band (Levon Helm). (John Sebastian was among Woodstock performers, but his music isn't featured on this particular episode.)