Their voices have graced many of rock's most famous songs and biggest tours, yet their names are unknown to all but those who read liner notes with the devotion of a theology student. They're the backup singers, and they're the subject of Morgan Neville's extraordinary new documentary, '20 Feet From Stardom.'

Throughout rock history, these singers -- nearly all of them African-American women -- have been called upon whenever artists wanted to connect with rock's gospel roots, either in the studio or on the road. Trained in the church (many were preachers' daughters), they quickly learned how to blend with the other members of the choir to sing as one voice. This served them well on sessions, where they could create their own arrangements and make immediate changes to their parts without needing to know how to read music.

Neville focuses largely on Darlene Love, Merry Clayton and Lisa Fischer, who give the movie's narrative continuity. Love mentored Clayton in the art of studio singing when Clayton left the road as one of Ray Charles' Raelettes, and Fischer has sung Clayton's iconic part on 'Gimme Shelter' for every Rolling Stones tour since 1989. In addition, such names as the Waters family, Claudia Lennear, Lynn Mabry and Tata Vega are brought in to tell their stories. Mick Jagger, Bruce Springsteen, Sting and other artists and producers are also interviewed to provide insight into their work and important place in music.

Born Darlene Wright, Love's story is a movie unto itself. Beginning as a teenager in the late '50s with the Blossoms, she provided harmonies on a variety of hits before becoming Phil Spector's ace in the hole, singing for both the Crystals and Bob B. Soxx and the Blue Jeans, and given an occasional solo track to keep her happy. Eventually she was so emotionally beaten down by Spector that she gave up singing and took a job cleaning houses to support her family. It was only after hearing her epic 'Christmas (Baby Please Come Home)' on the radio of one of her clients that she knew where she should be and resurrected her career. In 2010 she was inducted into the Rock and Roll Hall of Fame.

Clayton emerges as the best storyteller of the group. She gleefully plays up her diva image as she recounts how she came to record 'Gimme Shelter' (at which point her vocal solo is isolated, with reaction shots from both her and Jagger) and her initial reticence at recording Lynyrd Skynyrd's 'Sweet Home Alabama,' given the state's notorious history with civil rights.

Fischer, meanwhile, is, by everybody's account, the best singer of the bunch, for both her astonishing range and smarts in giving a song exactly what's needed. In one scene, she is alone in the studio and improvises some jazzy a cappella four-part harmony. Words can't do justice to how impressive this is.

Even though their work was mostly unheralded (and sometimes uncredited), all of the women seemed to have enjoyed their roles, collecting triple-scale fees on everything from jingles to smash hits and traveling the world with the biggest names in the business -- all while simultaneously avoiding the spotlight. And they all took considerable pride knowing that they were responsible for creating the vocal hooks to so many popular and timeless songs.

Eventually, though, the for-hire work slowed as times and technology changed, which caused many of them to quit the business (Lennear became a teacher) or launch solo careers. However, their vocal prowess and reputations rarely translated to chart success. Clayton's records on Lou Adler's Ode label made little impact (a compilation from those albums was recently released to capitalize on the movie). Others were dismissively told that that the pop world didn't need another Aretha Franklin, and Vega experienced outright discrimination because of her weight.

Apart from Patti Austin, who became a star in the '80s (and is not heavily featured in '20 Feet From Stardom'), Fischer had the most success, winning a Grammy in 1992 for her No. 11 hit, 'How Can I Ease the Pain.' But while recording her follow-up album, she realized she was uncomfortable in the spotlight and returned to session work and tours. (Incidentally, Fischer was given her break in the '80s by Luther Vandross, who, in turn, got his start singing on David Bowie's 'Young Americans.')

This tricky balance is currently being navigated by Judith Hill, a 29-year-old singer who reached the Top 8 on the most recent season of 'The Voice.' On the one hand, she's a very talented singer-songwriter who, with the right breaks, could be a massive star. But at the same time, the backup gigs are paying the bills. Her appearance in '20 Feet From Stardom' should help establish her name.

Fortunately for Hill, she has the support and love of the women who came before her. If there is any professional jealousy or backbiting between the singers, Neville deftly avoids it in favor of showing this community as a genuine -- forgive the wordplay, but there's no better way to describe it -- sisterhood. There are some complaints about women who were probably chosen more for their looks than their voices, but no names are mentioned. Their lives and careers all intertwined at some point, and there's nothing but respect all around.

Neville weaves all of these elements together through interviews, archival footage and studio sessions that appear to have been booked specifically for the movie. A minor quibble is that there is little chronology given. If you're not already familiar with the story, you could walk away thinking it took place within a brief time frame instead of over the course of more than 50 years.

Still, '20 Feet From Stardom' is an incredibly entertaining and moving film that should not be missed by any music fan who wants to dig deeper. Check the movie's website for dates and times. Clayton is appearing at some screenings with a Q&A session after the movie and is every bit as charming in person as she is in the movie. And if you're lucky enough to be called upon, ask her to sing a little something. Trust us on this.


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