The defining factor, the thing that turns it from a dark riff into a ritual, is Merry Clayton’s voice. A gospel and soul singer, with background vocals for many artists, including Ray Charles. She also had a role on the 80s TV show Cagney and Lacey, and played a maid in the film Maid To Order. In 2013 she appears in the documentary 20 Feet from Stardom and talks about her appearance on this song. The night story is specific, the Stones were recording late at night in Los Angeles and decided they needed a female vocalist to sing with Jagger on the track. They called her in the middle of the night. She was pregnant then. They brought her to the studio. She arrived with curlers in her hair and silk pajamas. Jagger explained she would be singing the line “Rape, murder, it’s just a shot away.” She did a take, then on the next she decided to “blow them out of this room”. She delivered it an octave higher, her voice cracking on “murder”. You can hear it around 3:04, and you can hear Jagger in the background shouting a “Whoo!” in admiration. Jagger himself has described the moment, they suddenly wanted someone in the middle of the night, she was around, she came with her curlers straight from bed, had to sing a really odd lyric, and she was great.