Great thread Larry. There is definitely a popular myth that learning music - formally or otherwise, theory, harmony, etc,and above all, serious practice, are only for us mortals without mojo. I'm certain that when T Bone did that little diminished chord and slid it down a half step, he knew what it was called, and why it fit harmonically with the tonic. It's not just the blues masters either. My favorite quote from Jerry Garcia is "You've got to know your arpeggios."