When The Beach Boys needed someone to fill in for their leader Brian Wilson, Campbell was the one who stepped up to fill his shoes. From December 1964 to March 1965, Campbell toured with the group across the country. He was in charge of playing bass guitar and even sang the falsetto harmony parts.
But Campbell's connections to the Beach Boys didn't end with that tour. He also played the guitar for their popular album Pet Sounds, which was released in 1966. Over the years, Campbell played on several other recordings for the Beach Boys as well.