Not all chords extend to 13th.... theory check

[joenovice]

I read a post a min. ago and this is what was said;

 

 

every mode of the major scale is, in fact, a 13th chord. And every 13th chord created is unique: I = Maj 13th = Ionian ii = minor/major 13th = Dorian ii3 = min 13th b9th = Phrygian IV = Maj 13th #11th = Lydian V = 13th (dominant 13th) = Mixolydian vi = min 13th = Aeolian vii = 1/2 dim 13th = Locrian

 

 

While I understand the logic behind this type of comment I would say that in practicallity this is not good theory.

 

Major chords are rarely true 13's. More often they are add6, 6/9, or something else. This is all because of the 11.

 

A major triad with the 11 usually sounds bad due to the clash of 3rd, 4th, and 5th scale degrees. Usually this is resolved by removing the 3rd and creating a sus.

 

Likewise the ii, vi, and vii chords never extend to the 13th due to the function of such notes. If you extend the vii chord to the 13 you end with with a dominate chord.

 

ex. key of G (vii: F#, A, C, E, D = D9/F#) (vi: E,G,B,D,C = Cmaj7/E) (ii: A,C,E,G,D= C6/9 or D9sus2)

 

You can find good substitutions by thinking of how extenstions relate to other chords but not all chords extend to 13 in practical usage.

[gennation]

Functionality on the guitar, four/five finger - seven notes, notes clashing, melody/harmony, etc...are reasons that not all 13 chords are played/used as theory states.

But in theory you can build all chords to the 13, to build the complete harmony structure of the scale. That's the theory.

But, based on the usability of these chords we end up with "best practices". Which lead us to "common chords".

But, this also leads us to MANY different ways something can be written...

which leads us right back to theory to decipher what chord the person was actually stating by extending the harmony to it's fullest. Which sends us up to some notes that just aren't going to fit nicely...

which tells us, to have a complete perspective, it's better to know all of these things to have a good understanding of harmony related to scales and chords...in theory and in practicality.