Merry Clayton’s isolated vocals in “Gimme Shelter,” from The Rolling Stones album Let It Bleed. The Stones called Merry Clayton in 1969 and asked her, having heard some of her work as a backup singer, to record a background track on this particular song. I guess The Stones had this crazy itch to get the song recorded, because they called her in the middle of the night, and she showed up in night clothes, she was several months pregnant, and trying to shake off some lethargy. But she recorded these incredible vocals like it was nothing, and The Stones and everybody who heard the song afterwards were pretty damn amazed.
Merry Clayton and so many other backup singers who were on the scene in the U.S. when Rock N’ Roll was getting big, they have these really interesting stories, and if you’re ever interested in learning about them then I recommend the documentary 20 Feet From Stardom about a million times over.