Making the beat go on in this song was Carol Kaye, who played bass at the session. One of the top Los Angeles studio musicians, Carol played on hundreds of records, including tracks for Phil Spector and Brian Wilson. She had recently switched from guitar to bass - Sonny Bono would often use her for electric 12-string fills. This song had a very sparse bass part written, which Carol elaborated into the key part of the instrumentation. She told Songfacts
it was one of her biggest creative contributions to a hit record. "It was a nothing song, and then the bass line kind of made that," said Carol. She added that it was only one chord, but its impact made her realize how important a bass line could be and inspired her to play more of the instrument.