I was reviewing the “Chord Extensions 9, 11, & 13” lesson. You show how to form the C13 by adding a 6 to the C9 chord, and in this instance dropping the G in the right hand (around 10:20).
My question: Is the only difference between this and a C6/9 the omission of the b7? I was just wondering because I can usually get the 13 quickly when I see it on a chart, but I always seem to stop and fiddle about thinking about the 6/9.
Hi @scott1, thanks for writing!
Great question,
First, always remember what function the chord has; in this case the difference between the 6/9 and the 13 chord is that 6/9 chord is functioning as a tonic (I), whereas the 13 is a dominant (V).
So, when you’re practicing chords, always remember that the only important notes of the chord are 3, 7 (or 6 in the case of 6/9) and the root, for example:
So, when you approach more complicated chords from this angle, you will begin to understand harmony better.
First, always think of it as a tonic, or as something that is steady.
Play simple 3-note voicings in every key using only 1, 3 and 7 or 6, here example in C, with both inversions:
After you are totally comfortable with this, you can add the 9th to the chord, again with 2 inversions:
The main point being; Learn to hear and understand the core of the chord first before the extra tension (9th, 11th 13th etc.).
This way you will build up your knowledge from the foundation of functional harmony, and this will help you with every step on the way.
-Tuomo
Thanks Tuomo for your quick and quite thorough response. I guess I was trying to complicate things by thinking first of the extensions instead of beginning with the basic three-note chord structure and then adding things on. Really pretty straightforward if you do it the right way. 
Again, many thanks.
Any time!
Let me know if you have any further questions,
-Tuomo
