Morgan Neville's excellent new documentary '20 Feet From Stardom' takes a look at the role the professional backup singer has played in rock music. Steeped in gospel music, these predominantly African-American women were frequently called into the studio or out on to the road any time an act wanted to bring a bit of the church into their sound. Although they've been responsible for some of the hooks on some of rock's greatest records, they often weren't credited and, when they tried to use their reputations to start a solo career, they were mostly unable to translate their vocal gifts into commercial success. The movie got us thinking about our favorite vocal cameos. In some cases, these are the same women featured in the film, and in others they're established stars making a guest appearance on someone else's record. These aren't duets -- we've already covered that -- but rather moments where an equally distinctive voice was called upon to give the song a little something extra. With that criteria established, here is our list of the Top 10 Vocal Cameos.

  • 10

    Aimee Mann

    'Time Stand Still' (1987)

    Rush

    We begin our list of the Top 10 Vocal Cameos with a bit of an odd pairing. Eyebrows were raised when Aimee Mann, a darling of the New Wave for her hit 'Voices Carry' with her band 'til Tuesday, joined forces with the reigning kings of prog rock. But the singer, who has gone on to record many excellent solo albums over the past 20 years, sings the titular lyric and her harmony lines with Geddy Lee with aplomb, providing a bit of warmth for a band often derided for choosing precision over emotion.

  • 9

    Linda Ronstadt

    'Under African Skies' (1985)

    Paul Simon

    Paul Simon's 'Graceland' album introduced much of the world to the music of South Africa in the last few years of the apartheid era. And while the contributions by Ladysmith Black Mambazo and the other musicians received deserved praise and gave them a worldwide audience, Ronstadt's work on 'Under African Skies,' also stood out. The song's second verse was inspired by Ronstadt's childhood growing up in Tuscon, Ariz.

  • 8

    Tom Petty

    'Sea of Heartbreak' (1997)

    Johnny Cash

    For 'Unchained,' the second album Johnny Cash recorded during his mid-'90s comeback, producer Rick Rubin brought in Tom Petty and the Heartbreakers to serve as his backup band. Although the group stuck to their instruments for most of the record (because who needs other singers with Cash around?), Petty stepped forward on the chorus of Don Gibson's country classic and matched the Man in Black note-for-note. Twelve years later, Cash's daughter Rosanne Cash recorded a lovely version of the same song, with Bruce Springsteen crooning along.

  • 7

    Neil Young

    'Splendid Isolation' (1989)

    Warren Zevon

    'Transverse City,' a synth-heavy science fiction-influenced concept album, wasn't a high point of Warren Zevon's career. But it contained one of his most beloved tunes in 'Splendid Isolation,' where Neil Young, no stranger to telling people to leave him alone, contributes vocals and harmonica to the song.

  • 6

    Mick Jagger

    'You're So Vain' (1972)

    Carly Simon

    He wasn't credited, but there's no mistaking the voice that doubles Carly Simon's lead vocal in the chorus of her smash hit. In what could also be called the "Battle of the Dueling Lips," Jagger's performance led many to speculate that the song was written about him, but Simon has always denied the rumor.

  • 5

    Claire Torry

    'The Great Gig In The Sky’ (1973)

    Pink Floyd

    The second half of our list of the Top 10 Vocal Cameos begins with a wordless vocal that closes out the first side of 'The Dark Side of the Moon.' For almost four minutes, Torry wails against a Richard Wright chord progression, occasionally reaching stratospheric heights. Although she was paid only the standard rate for a session, she sued the band in 2004, claiming that her improvised part amounted to co-authorship of the song. A settlement was reached a year later that gave her co-credit.

  • 4

    Sandy Denny

    'The Battle of Evermore' (1971)

    Led Zeppelin

    Sandy Denny was the lead singer in Fairport Convention, a band that electrified traditional British folk music -- similar to what the Byrds did for American folk. Although the group never achieved mainstream success, Denny's haunting vocals wound up on one of the most popular albums of all time, where she showed that she's more than capable of holding her own with Robert Plant. Fairport Convention also launched the career of guitarist extraordinaire Richard Thompson.

  • 3

    Sting

    'Money for Nothing' (1985)

    Dire Straits

    Mark Knopfler wrote 'Money for Nothing' as a satire in the persona of a blue-collar guy watching MTV with disdain, so who better to drive home the point than one of the biggest stars on the music network? Sting contributed his distinctive voice throughout the song. When his coda of "I want my MTV" sounded too much like the Police's 'Don't Stand So Close to Me,' Knopfler gave Sting a co-writing credit.

  • 2

    Maggie Bell

    'Every Picture Tells a Story' (1971)

    Rod Stewart

    If you didn't jump out of your seat the first time you heard Maggie Bell, in the persona of Shanghai Lil, claim that using birth control "just ain't natural," you probably weren't listening hard enough to 'Every Picture Tells a Story.' On the album of the same name, Bell is credited with providing "vocal abrasives." At the time, she was also the lead singer of Stone the Crows, a Scottish blues-rock band that included future Wings guitarist Jimmy McCulloch.

  • 1

    Merry Clayton

    'Gimme Shelter' (1969)

    The Rolling Stones

    The highlight of the 2013 documentary '20 Feet From Stardom' is when Merry Clayton tells the story of how she came to record her iconic part on 'Gimme Shelter,' which tops our list of the Top 10 Vocal Cameos. She received a call from arranger Jack Nitzche just as she was getting ready for bed. Throwing on a coat and a scarf over her pajamas and hair curlers, she went down to the studio and, in a few takes, created one of the most chilling moments in rock history. The two times her voice breaks in her solo serve as a cry for sanity amid the turbulence of the late '60s. Oh, and she was also very pregnant during the session.