C13 = C, E, G, Bb, D, F, A.

It's got the notes 1, 3, 5, b7, 9, 11, 13. Note the flatted 7th, since this functions as a dominant chord.

That's a lot of notes, so you'll typically leave a few out.

The mandatory notes are C (defines the root), Bb (defines the dominant function) and A (wouldn't be an 11th without it). An E (the 3rd) is usually a good idea, because it tells you if the chord is major or minor.

On the other hand, the notes D (9th) and F (11th) are generally considered non-essential tension notes, so they are optional. And since there's no altered 5th, the G is optional as well.


-- David Cuny
My virtual singer development blog

Vocal control, you say. Never heard of it. Is that some kind of ProTools thing?