The Song With No Words
Despite its haunting power, this Pink Floyd classic contains no lyrics. The legendary vocal performance was entirely improvised by a session singer who was told simply to think about death.
During the recording, Clare Torry had no direction other than to improvise over the piano chords. She was so embarrassed by her emotional performance that she apologized to the band before leaving the studio. The band loved it so much they kept the first take exactly as it was. It remains one of the few moments in the band's history where they handed the spotlight to an outside guest.
Source: The Great Gig in the Sky