Theory posse – we’ve looked at major and several types of minor scales… We’ve seen the minor to major relationship…. We’ve figured out the chords from the major scale up to the 7th and seen that they are related to the natural minor….. so let’s take the chords a little further and look at the ‘extensions’, the 9th, 11th and 13th over various 7th chords….
What do the 9th, 11th and 13th represent?
Using the key of G major, we worked out the chord of G^7 [root, major 3rd, perfect 5th, major 7th]
T 2 3 4 5 6 7
scale = G, A, B, C, D, E, F#…..
R 3 5 7
G^7 chord = G, B, D, F#
Given that chords ‘stack’ in 3rd’s then we can work out these extensions by running back though the notes of the scale and keep counting…..
T--2 --3---4--5--6---7---8---9--10--11-12-13-14
scale = G--A--B--C--D--E--F#--G--A--B--C--D--E--F#
G^9 [spoken G major nine] is built upon the G^7 with the addition of the 9th and is therefore calculated from the G major scale so the 9th is A. [G, B, D, F#, A]
G^11 [spoken G major eleven] is built upon the G^7 with the addition of the 9th and 11th and is therefore calculated from the G major scale so the 9th is A and the 11th is C. [G, B, D, F#, A, C]
G^13 [spoken G major thirteen] is built upon the G^7 with the addition of the 9th, 11th and 13th and is therefore calculated from the G major scale so the 9th is A, 11th is C and the 13th is E. [G, B, D, F#, A, C, E]
If the triad G had for example a 9th but no 7th, it would be G add 9 [a G chord with the 9th added to it] – G, B, D, A
Similarly, if G^7 had for example a 13th but no 9th and 11th it would be G^7 add 13 [a G^7 chord with the 13th added to it] – G, B, D, F#, E
the main point to note here is that G^x is calculated from the key of G major.
The ‘minor’ extended chords follow exactly the same rules [built on top of Em7] but this time the notes are calculated from the minor scale…..
Em11 [spoken E minor eleven] is therefore worked out from the key of Em and is E, G, B, D, F#, A
Em9 add 13 [spoken E minor nine add thirteen] is an Em9 chord with the 13th added [so it has no 11th] – E, G, B, D, F#, C. [no A]
Getting the idea??????
I know that some jazzers use for example the 6th instead of the 13th sometimes and say that they chose this due to the octave that the note was in… i.e. how close it is to the root….. this is not how I learned this stuff…. The octave is not relevant and this is why…..
It is possible to have a root, then a 5th above and the a 3rd above the 5th [which means it is in the next octave].. This is ‘voicing’ – choosing how you want to arrange the notes for a particular effect… so this triad would still be G and not G5 add 10 [which is trying to say ‘a G chord with no 3rd, a 5th and a 10th added in from the next octave performing the function of the 3rd’…. way too ugly]…
This being the case, G, B, D, E would be G add 13 and not G major 6 or G add 6 [although many jazzers would write it this way] – don’t forget, I went to a different ‘school’…. The main point here is to be aware of conventions… to me, odd numbers describe individual chords, even numbers describe a suspension which is not a single chord but part of a progression [which I’ll cover later]..