The band was formed by husband and wife John and Michelle (Gilliam) Phillips, formerly of the New Journeymen, and Denny Doherty, formerly of the Mugwumps. Both these acts were active during the last years of the Great Folk Revival of the Fifties. The last member to join was Cass Elliot (Miriam Cohen), Doherty’s band mate from the Mugwumps, who had to overcome John Phillips’ concern that her voice was too low, that her physical appearance would be a turnoff, and that her temperament was incompatible with his. They considered calling themselves the Magic Cyrcle before switching to the Mamas and the Papas, inspired by the Hells Angels, whose female associates were called “mamas.”
They spent the much of 1965 in the Virgin Islands to rehearse and put everything together. John acknowledged that he was reluctant to abandon folk music. Denny said he hung on to it “like death.” Roger McGuinn: “It was hard for John to break out of folk music, because I think he was real good at it, conservative, and successful, too.” John acknowledged that it was Denny and Cass who awakened him to the potential of contemporary pop. While the New Journeymen had played acoustic folk and the Mugwumps played something closer to folk rock, their rehearsals in the Virgin Islands were “the first time that we tried playing electric.” Considering that Bob Dylan and the Byrds were paving the way in 1965, this should not have been a surprise.
The band traveled to Los Angeles for an audition with Lou Adler, co-owner of Dunhill Records. The audition was arranged by former New Christy Minstrel Barry McGuire, who had befriended Cass and John independently over the previous years and who had recently signed with Dunhill in a deal that would see the success of P. F. Sloan’s song “Eve of Destruction.” It led to a deal in which they would record two albums a year for the next five years with a royalty of 5 percent on 90 percent of retail sales. Dunhill tied the band to management and publishing deals, commonly known as a “triple hat” relationship. Cass’ membership was not formalized until the paperwork was signed, with Adler, Michelle and Denny overruling John.
The Mamas and the Papas made their inaugural recording singing background vocals on McGuire’s album “This Precious Time,” although they had already released a single of their own by the time the album appeared in December 1965. This single was “Go Where You Wanna Go,” which was given a limited release in November but failed to chart. The 5th Dimension would later turn it into a hit.
From the beginning, the band was backed by the Wrecking Crew with a string component. Among the musicians in these sessions were Tommy Tedesco, Carol Kaye, Larry Knechtel and Hal Blaine.