As a future jazzmando head, I am trying to figure this out, so I figured I would go ahead and ask.... The chord (for example) A13, the 13th note is a F#, which is also the 6th. Is the difference b/t A6 and A13 the flattened 7th and "6th" note (or 13) on the A13. If so, does this mean that 9, 11 and 13 chords always have a flattened 7th (unless maj7 or min7)? Am I on the right track?