"Aquarius/Let the Sunshine In" is a medley of the songs "Aquarius" and "The Flesh Failures (Let The Sunshine In)" from the musical Hair, originally released by the The 5th Dimension as a single which held the #1 position on the U.S. charts for six weeks in 1969. The recording won the Grammy Award for Record of the Year and Best Contemporary Vocal Performance by a Group at the Grammy Awards of 1970, after it was released on the album The Age of Aquarius.

This song became a radio hit. It is still heard on oldies radio stations.