"Gimme Shelter" (The Rolling Stones)

"Gimme Shelter" opens The Rolling Stones' 1969 album Let It Bleed and essentially slams the book closed on the hippie utopian dream.  Mick Jagger and the boys take a look at the world around them, and what they see is pretty bleak: war, rape, and murder—all just a shot away.
As Jagger told NPR's Melissa Block back in 2012, "It was a very moody piece about the world closing in on you a bit. When it was recorded, early '69 or something, it was a time of war and tension, so that's reflected in this tune."
What's also reflected in the tune is their "back to basics" approach to crafting raunchy R&B, a reboot that began with their 1968 album, Beggar's Banquet.  From the moment Jagger coos his eerie falsetto oooh's atop that undulating Latin-flavored intro to the final seconds of his smoldering blues harmonica in the fadeout, it's clear that they were no longer interested in aping The Beatles.
The most memorable moment of the song, though, doesn't even come from any of the Stones; it comes from backup singer Merry Clayton.
The band was putting the finishing touches on the song in Los Angeles in the middle of the night, when Jagger and partner in crime Keith Richards decided it needed a female vocal.  Story goes, they'd tried to contact a number of vocalists and finally ended up reaching (a very pregnant) Clayton as she was on her way to bed.  They convinced her to come to the studio—still in her silk pajamas with a scarf covering the rollers in her hair—to cut some vocals.
Thing is, she had no clue who they were!  All she knew was that they were some little rock outfit from England.  So, understandably, she was taken aback when she got there and found out they wanted her to belt out the unsavory lyrics: Rape, murder / It's just a shot away.  Nevertheless, she did a solid take, vamping and singing along with Jagger's lead.
Impressed with her confidence and swagger, Jagger asked if she was up for another take.
As Clayton reminisces in the fantastic 2013 documentary 20 Feet from Stardom, "I said to myself, 'I'm gonna do another one, and I'm gonna blow them out of this room'."
That's when she unleashed the now-famous gospel-tinged shout that sounds like someone crying out in the wilderness.  It's not just sung; it's wailed, complete with cracks and breaks—particularly when she hits the word murder.  It's one of the most frightening, exhilarating things ever captured on tape.
Clayton's singular performance takes a good track that would have been a decent snapshot of its time and crystallizes it into the definitive chronicle of its era.