Also featured in the film are Claudia Lennear, who is said to be the inspiration for both the Stones' "Brown Sugar" and David Bowie's "Lady Grinning Soul" and who posed for Playboy in 1972, plus Tata Vega, vocalist for Stevie Wonder, and Judith Hill, former Michael Jackson singer turned solo artist.
"All of these women are playing off the classic Lou Reedian idea of the backup singer," says Neville, a 1989 University of Pennsylvania grad who's produced music docs on Johnny Cash, James Brown, and the Stones.
Speaking from his home in Los Angeles, Neville is referring to the "Wild Side" classic call-and-response in which Reed, in his 1972 hit, talk-sings the line "and the colored girls say" and a trio of black female voices reply "doo do doo, doo do doo, doo do do doo."
"It's the idea of iconic African American voices, three women on the side of the stage in black dresses, bringing the church," he says.
Fischer, who sat for a lunchtime interview in Philadelphia the day after the first Stones gig last week, is "the backup singer's backup singer," says Neville.
The first rule of backup singing is that "it's about the music, first," says Fischer. "You're not there to be their best friend."
In addition to performing with Jagger, the dazzling-voiced Brooklyn-born singer, who got her start as a member of latter-day versions of the Crystals and Marvellettes, has sung with Luther Vandross, Chris Botti, and Sting. The latter, when asked about her in 20 Feet, merely says her name and shakes his head in amazement.
When she stepped up to look Jagger in the eye and belt out "Gimme Shelter" at the first Wells Fargo show, one woman in the audience, unable to contain her enthusiasm, exclaimed: "She's so good!" That's a fairly typical reaction to Fischer's talent.
Fischer revels in that moment in each performance. "When I'm up there and I'm singing that, I'm thinking to myself, 'I wish you could feel what's in my body at this moment.' I am trying so hard to radiate this energy to [the audience] so they can get it. It's just amazing. It's such a gift."
Twenty Feet wrestles with the question of why many talented backup vocalists, many of whom are better singers than their superstar employers, never get their own place in the spotlight.
The 54-year-old Fischer refers to Love and Clayton as "my maternal sisterhood. They had a different fight than I did." The most egregious music-business crimes in the film are perpetrated on Love by Spector, who used her voice on songs like "He's Sure the Boy I Love," then credited it to the Crystals. "She was wronged," says Fischer.
But there are other obstacles beyond injustice. Stardom requires ego. "You got to have that narcissism," Bruce Springsteen says in the film. Love echoes that idea, saying, "You have to have that kill spirit." Though everyone agrees Clayton had the talent and the attitude - in the movie, she recalls thinking in the 1970s, "When it came to my project, I was going to kick ass and take names" - she never broke through. "If she had one hit," says Neville, "she would have been Patti LaBelle or Chaka Khan."
Fischer is a unique case. She scored solo success with her 1991 album, So Intense, and won a Grammy for the No. 1 R&B hit "How Can I Ease the Pain."
That song title hints, though, at Fischer's preference for playing a supporting rather than leading role.
"The industry is for those who are willing to put themselves on display," she says in the film. "Ambition is higher up on the list than talent" when it comes to making it, adds Neville, on the phone. "It's not about ambition for Lisa. She's not driven that way."
When it came time to follow up So Intense, changes at Fischer's record label resulted in "people trying to pull me in different directions that I wasn't sure were right for me," she says. "My mind-set was more of fitting into something than leading the charge." She never finished the album, and has no regrets.
"I'm good," she says.
Things might be about to get better for the women of 20 Feet From Stardom, due to the buzz about the movie, which was a collaborative idea between Neville and legendary behind-the-scenes record man Gil Friesen, who died last year.
My Name Is Love, the singer's memoir, has been reissued. Columbia is putting out a Best of Merry Clayton compilation on July 9. Judith Hill is playing the Social at Revel casino in Atlantic City on July 12 and 13. And Phew!, Lennear's 1973 solo album, is due out on CD for the first time in September.
A 20 Feet From Stardom sound track was released this week. "I hope that these ladies go on tour, have records, and that everything that should come to them does come to them," says Neville.
With the renewed attention, Fischer, who spent much of her down time on the Stones tour doing interviews for the movie, says she's open to working on new collaborative ideas. But another crack at a solo career is not a priority.
"When I go into the studio, whether I'm singing for people or I'm singing lead, it's still supportive in my mind," she says. "It's not a solo energy. It's a sharing energy for me. I just want to create beautiful music. I really do. My priority is to be happy, and what makes me happy is to sing."
20 Feet From Stardom
Opens Friday at the Ritz Five
Contact Dan DeLuca at 215-854-5628, firstname.lastname@example.org, or follow on Twitter @delucadan. Read his blog, "In the Mix," at www.inquirer.com/inthemix.