She was born on August 18 1945 in Trenton, New Jersey, the seventh of 13 children; her mother was a nurse, her father a pastor. Her musical roots were in gospel, but at a tender age she formed a vocal duo, the Del-Capris, with Nona Hendryx.

In the early 1960s they were recruited, along with Cindy Birdsong, by the Philadelphia singer Patti Holt for her band, the Ordettes. They became the Blue Belles, and had a Top 20 hit with their 1962 debut, I Sold My Heart to the Junkman. Patti Labelle later confessed that the song had actually been recorded by another band, the Starlets, and their manager was sued after the Blue Belles lip-synched to the disc on the American Bandstand TV show.

ecovering from the controversy (unlike the Starlets, who disbanded), the Blue Belles cemented their reputation as a storming live act, opening for the Stones on their 1965 US tour, and they had a genuine hit of their own with the doo-wop ballad Down the Aisle (the Wedding Song).

They toured Europe, appearing on Ready Steady Go and playing dates supported by Bluesology, whose pianist was Reg Dwight, later Elton John. In 1967 Cindy Birdsong departed to join the Supremes, but the Blue Belles’ career stepped up a gear when Dusty Springfield told Vicki Wickham – the manager and Ready, Steady, Go! producer who had written the lyrics to You Don’t Have to Say You Love Me – that she should take the group on.

© Provided by The Telegraph Labelle c. 1970 - RB/Redferns

She wrought immediate changes, shortening their name to Labelle, and advising the band to incorporate the seams of funk, rock and psychedelic soul that bands like Sly and the Family Stone and the Temptations were successfully mining.

She signed them to The Who’s Track label, whose New York office she was running, and guided their career alongside the British band’s managers Kit Lambert and Chris Stamp. In 1971, ditching their ballgowns for denim and Afros, Labelle opened for The Who on their US tour. The same year came their acclaimed self-titled debut album, followed in 1972 by Moon Shadow.

Labelle also sang backing vocals for Laura Nyro, then in 1973 they released the popular LP Pressure Cookin’. But the real breakthrough came in 1974: changing their image again, to a glam rock look, they recorded their masterpiece, the rock’n’soul Nightbirds album, produced by Allen Toussaint.

The lead single, the raunchy Lady Marmalade, with its celebrated chorus, “Voulez-vous coucher avec moi, ce soir?”, became their first No 1, while Nightbirds went gold. Labelle became the first rock band to play the Metropolitan Opera House in New York and the first African-American vocal group to feature on the cover of Rolling Stone. They sang backing vocals on Elton John’s Rock of the Westies album and released two more of their own, Phoenix and Chameleon.

But there were no more hit singles, and the classic “creative tensions” were very real: Patti LaBelle wanted more soul, Nona Hendryx favoured funk rock, while Sarah Dash craved disco hits.

The end came during a show in Baltimore in December 1976, when Nona Hendryx wandered off stage and into the audience. The stage manager led her backstage, but the singer locked herself in the dressing room and began smashing her head against the wall; she was eventually restrained and taken to hospital, and Patti Labelle suggested that for the good of everyone’s mental health the band should split.

Sarah Dash had some success with the disco single Sinner Man, and went on to provide backing vocals on the Rolling Stones album Steel Wheels, as well as working with Keith Richards on his spin-off project X-pensive Winos.

There were several Labelle reunions over the years, producing a 1995 dance hit, Turn it Out, and culminating in a much praised album Back to Now (2008). Two days before her death, Sarah Dash joined Patti Labelle on stage in Atlantic City.

She was married briefly to the saxophonist Sam Reed.