Gladys Knight & The Pips, "Everybody Needs Love" (1967)

You must have seen the documentary 20 Feet from Stardom. It's about backup singers, many of whom learned to sing in choirs where their fathers were preachers, and the difficulty of making the transition from backup singer to lead. It's got, in addition gorgeous vocals, interesting commentary from the likes of Mick Jagger and Bruce Springsteen.

P.S. I realize now that background describes Aretha Franklin and sort-of Gladys Knight; anyway, it came to mind.