"Medley: Aquarius/Let the Sunshine In (The Flesh Failures)" (commonly called "Aquarius/Let the Sunshine In", "The Age of Aquarius" or "Let the Sunshine In") is a medley of two songs written for the 1967 musical Hair by James Rado and Gerome Ragni (lyrics), and Galt MacDermot (music), released as a single by American R&B group the 5th Dimension. The song spent six weeks at number one on the US Billboard Hot 100 pop singles chart in the spring of 1969 and was eventually certified platinum in the US by the RIAA. Instrumental backing was written by Bill Holman and provided by session musicians commonly known as the Wrecking Crew. The actual recording was novel at the time, being recorded in two cities, Los Angeles and Las Vegas, and being mixed down to a final version later. The song listed at number 66 on Billboards "Greatest Songs of All Time". History The recording was led by veteran American producer and engineer Bones Howe, who had previously worked with the 5th Dimension as well as the Mamas & the Papas and Elvis Presley. As Howe tells it, the recording can be traced to an incident in which 5th Dimension lead singer Billy Davis Jr. left his wallet in a New York City cab; the man who found the wallet was involved in the production of Hair and invited the group to see the show: "After they'd seen it I received a phone call in which they were all talking over one another, saying 'We've got to cut this song "Aquarius". It's the best thing ever.'" Howe was skeptical ("This isn't a complete song. It's an introduction."), but after seeing the show on stage got the idea to create a medley with another musical moment from the show, a few bars from the song "The Flesh Failures" that consist of the repeated words "let the sunshine in." Although the two song fragments are in different keys and tempos, Howe resolved to "jam them together like two trains." The instrumental track was set to tape at Wally Heider's Studio 3 in Hollywood by the Wrecking Crew members including Hal Blaine on drums, Joe Osborn on bass, Larry Knechtel on keyboards, Tommy Tedesco and Dennis Budimir on guitars and Tony Terran on trumpet. It also featured strings, winds, and brass instrumentations. However, the vocals were recorded separately in Las Vegas, where the 5th Dimension was performing