God Only Knows: Vocal Harmony - The Voice (2003)

Documentary examining the different types of music that require vocal harmony and how much of what we know as pop music--rock, R&B, etc.--actually developed from gospel and religious music. Included is footage from many vocal groups from the 1950s and 1960s that were renowned for their smooth harmonies, such as The Moonglows, The Supremes, The Staple Singers and The Beach Boys.