Before he had any national recognition by the public, he was a member or the "Wrecking Crew" along with Leon Russell, and others.
He played guitar with the Beach Boys when recording, and went on tour too.
He was one of the first truly cross-over "country" types, into "pop" and "rock."
Others have included (but not limited to) Elvis, Johnny Cash, Willie Nelson etc. Plus Linda Ronstadt. In my opinion.