The term 'Half a 1960s Quartet' refers to the two members of the musical group The Mamas and the PAPAS, which was active in the 1960s. The two members are Mama Cass Elliot and Papa John Phillips. The Mamas and the PAPAS were an American folk rock vocal group that rose to fame in the mid-1960s with their popular singles such as 'California Dreamin'', 'Monday, Monday', and 'Dedicated to the One I Love'. They were known for their close harmonies and lyrics that reflected the counterculture of the time.