No surprise there. Seems everyone played with everyone at some point. Many who became solo artists and/or long term group members had started as studio musicians. During an interview Jim Stafford, being self-taught, modestly stated that he could work his way around multiple instruments. "I would watch someone else do a chord or a run and think, "I could do that", then attempt to imitate it, practice it, put my own spin on it". Personally, I feel Glen Cambell (also studio musician) should have stuck to his guitar and never sang a word. It was his appearance and diction that led to his own TV show.
