Phil Ford has a post wondering about the self that performs.
Kyle Gann talks about ego involvement in talking vs. composing.
Between the two I have the notion there's a deep insight here to be grasped, that goes to the heart of what I think music therapy can be. Trungpa Rinpoche said somewhere in one of his books that if you really want to see your ego, look within at the moment someone falsely accuses you of wrongdoing. A big part of that reaction, at least for me, is a verbal explosion, an explaining of why the accusation is wrong. It's also the exact opposite of what Phil Ford is talking about when the self fades and the flow takes over when performing, and the mental verbal chatter ceases for a while.