I think 13 is enough to keep track of. And yes, Gordon, add X means only that is X added to a triad, and other normally implied notes are not there. So I would expect Gadd9 to not have the seventh of the chord. Likewise, I expect, as you do, that a 13th chord can have, but may not have, a 7, 9 and / or 11 in it. But it almost certainly will sound the seventh, to give it that "flavor".


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