Upon hearing about the death of Bobby Keys, the longtime Rolling Stones saxophonist, my mind immediately went to last year's Academy Award-winning hit documentary 20 Feet from Stardom. While Keys wasn't featured, the film is about the back-up singers who voices gave rock music its heft.

Toward the middle of the movie, there is a particularly unforgettable moment in which singer Merry Clayton tells the story of how she came to belt out the most iconic part of the Rolling Stones classic "Gimme Shelter." During the scene, Clayton's vocals are isolated from the track so they could be heard on their own. The effect is both haunting and stunning:

One takeaway is that when Clayton's voice is removed from the Stones' instruments, it showcases how much more impressive her voice is than a listener first thought.

Bobby Keys, who died at 70, spent over 40 of those years recording and touring with the Rolling Stones. As NPR points out, the Texas-born reed player also had stints with the likes of John Lennon, Carly Simon, B.B. King, Joe Cocker, and others. Still not impressed? Consider that Keys "actually got kicked out of the Rolling Stones for partying too hard in the 1970s."

Keys also backed the Stones on the band's fabled three-album blitz from Let It Bleed to Exile on Main St., arguably the Stones' best era. As a sideman, he was also in the near vicinity of stardom, but his work leaves a different imprint on the music. On "Can't You Hear Me Knocking," unlike Merry Clayton's voice, Keys' saxophone bleeds into the rest of the sound in a way that would be foolish to isolate, making the song's sum not just better, but fuller than its parts:

In a statement on Tuesday, Stones guitarist Keith Richards said of Keys:

I have lost the largest pal in the world and I can't express the sense of sadness I feel, although Bobby would tell me to cheer up. My condolences to all that knew him and his love of music.

Speaking of love, for one of rock's best saxophone solos, look past Mick's transfixing yellow pants (if you can) and watch Keys play his classic part on "Brown Sugar."

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