One of the most commercially successful folk-rock groups of the mid-1960s, the Mamas and the Papas were known for their rich vocal harmonies as well as their unconventional appearance. The group's four founding members only sang together for a few years, but their recordings, which included nine Top Forty hits, made a lasting impact on pop music. Their first single, "California Dreamin'," established them as part of a new Los Angeles-based hippie music scene, even though they initially came together as a folk act in New York's Greenwich Village. Few pop groups featured a combination of male and female voices, and this rare sound became a factor in the Mamas and the Papas' popularity among adults. During the early 1960s, pop music was designed primarily for teenagers. With the advent of performers like the Mamas and the Papas, who...