Stars Who Were Once Backup Singers

[Carl]

Putting together Roger's interview with Darlene Love, where she talks about how being a backup singer can be a good career move, even today. That got me thinking about some of the singers who made the leap from singing backup to becoming superstars. The biggest names I can think of are:

Mariah Carey, who was a backup singer for Brenda K. Starr.

Sheryl Crow, who sang backup for Michael Jackson.

Who are some others?