From what I was told, he couldn’t read music. But he sure could play it.
Don’t know if he could read music, if not it wouldn’t surprise me. Do know he was one of a group of studio musicians known as the wrecking crew, who did sessions for hoards of musicians, including the Beach Boys.
I kind of doubt that, as he was one of the top west coast studio musicians before his solo career. He was a member of "The Wrecking Crew," and played on movie & TV soundtracks, and albums from Frank Sinatra to The Beach Boys.