The Mamas & the Papas

From Wikipedia:

The Mamas & the Papas was a folk rock vocal group formed in Los Angeles, California, which recorded and performed from 1965 to 1968. The group was a defining force in the music scene of the counterculture of the 1960s. The group consisted of Americans John Phillips, Cass Elliot, and Michelle Phillips, and Canadian Denny Doherty. Its sound was based on vocal harmonies arranged by John Phillips, the songwriter, musician, and leader of the group, who adapted folk to the new beat style of the early 1960s.

The Mamas & the Papas released five studio albums and 17 singles over four years, six of which made the Billboard top 10, and have sold close to 40 million records worldwide. The band was inducted into the Rock and Roll Hall of Fame in 1998 for its contributions to the music industry. The band reunited briefly to record the album People Like Us in 1971 but had ceased touring and performing by that time. Some of their most popular singles include “California Dreamin'”, “Monday, Monday”, and “Dedicated to the One I Love”. […]

In June 1966, The Mamas & the Papas travelled to London for a promotional visit. On June 12, they went to the discotheque Dolly’s and met with John Lennon and Paul McCartney. Some days later, George Harrison invited them to his Esher’s home; Paul McCartney joined them in the evening.

Paul McCartney and George Harrison met with members of the band again in August 1966, when The Beatles were in the US for their last tour.

In April 1967, Paul was in the US to spend some days with his girlfriend Jane Asher and was invited to John and Michelle Phillips’ house.