I'd known he was a mega sessions player and played on some of the biggest hits out there in the 60's but was surprised to find out
the Beach Boys actually wanted Campbell to join the band after he toured with them but he was already working on his solo career.
"Campbell's guitar acumen and versatility made him an essential player on Los Angeles' thriving recording scene in the 1960s as part of the loose-knit session musician collective the Wrecking Crew, and he contributed to sessions for Frank Sinatra, Dean Martin, Rick Nelson, The Mamas and the Papas, Merle Haggard and many more. Campbell couldn’t read music, but he quickly became a respected, first-call player.
He played on Elvis Presley’s “Viva Las Vegas,” The Monkees’ “I'm a Believer,” Sinatra’s “Strangers in the Night” and more. He played 12-string guitar on the Beach Boys’ “Sloop John B.,” and toured with the Beach Boys in 1965, as a replacement for the band’s troubled and reclusive leader, Brian Wilson.
Campbell was invited to join the Beach Boys as a full-time member in 1965, but he declined that opportunity. By then, he was set on establishing a solo career of his own."
Glen Campbell, 'Rhinestone Cowboy' singer, dead at 81