The untold true story of the backup singers behind some of the greatest musical legends of the 21st century. Triumphant and heartbreaking in equal measure, the film is both a tribute to the unsung voices who brought shape and style to popular music and a reflection on the conflicts, sacrifices and rewards of a career spent harmonizing with others. These gifted artists span a range of styles, genres and eras of popular music, but each has a uniquely fascinating and personal story to share of life spent in the shadows of superstardom. Along with rare archival footage and a peerless soundtrack are intimate interviews with Bruce Springsteen, Stevie Wonder, Mick Jagger and Sting to name just a few.