From Wikipedia
“1960–66: Early career[edit]
In 1960, Campbell moved to Los Angeles to become a session musician.[9][10] Around this time he was part of the group The Champs. Soon, Campbell was in great demand as a session musician. He was part of a group of studio musicians who became known as The Wrecking Crew.[10][11] During this period he played on recordings by Bobby Darin, Ricky Nelson, Dean Martin, Nat King Cole, The Monkees, Nancy Sinatra, Merle Haggard, Jan and Dean,[9] Elvis Presley,[12] Frank Sinatra and Phil Spector.”
Here’s a link to The Wrecking Crew
http://en.wikipedia.org/wiki/The_Wrecking_Crew_(music)