[dfwgator]

I've read that Greg Allman is uncredited on many famous records. They say he'd show up when asked, play his heart out and leave with a bag of cash.

Are you sure you're not thinking of Leon Russell, who was a member of "The Wrecking Crew"?

[FredZarguna]

No, he’s thinking of Duane Allman, not Gregg. Duane was a session player on many fine performances, both credited and uncredited.

[blam]

Leon left us in November 2016:

Leon Russell dies.