Chords Construction – Addendum
“Chord Extensions Finder” Technique
This is the last (and added after the fact!) page about how to construct chords… in fact, this jazz chord extensions primer can help you visualize both the components of chords AND scales… extensions are both vertically and horizontal! (-:
What you should know beforehand: since this jazz chord extensions page was added later, you should understand roughly how scales, modes, triads, 7th chords and chord with extensions are built (or else you won’t be able to apply the process described on this page).
In the course of this jazz theory article series about chord construction, you’ll find music theory info about triads and sevenths chords, how to add extensions, chord equivalents, diatonic chords and finally a neat theoretical process to understand what extensions are “allowed” on jazz chords.
Jump to a page:
Chord Construction 1: Triads and Sevenths
Chord Construction 2: Adding Extensions
Chord Construction 3: Equivalents
Chord Construction 4: Chords from three scales
Addendum: The “Chord Extensions Finder” Technique [You’re Here]
- What is a “b9”? Answer: the interval that consists of the distance of 13 half-steps between two notes. For instance: E to F (the latter being an octave higher). In fact, you can think of the “b9” as a minor second with octave displacement: a half-step for wich the highest note is “up the octave”.
- Extensions: on this page, extensions are considered the tones 9, 11 and 13 (including alterations of them, such as #9, b13 and so on.)
- Scales and Modes: The process below can be applied to any scale or mode, but it’s best to start with all the chords in the major, melodic minor and harmonic minor scales first…
Jazz Chord Extensions: Why This Process?
The process described in the following paragraphs will allow you to find (yourself) what extensions “are good” (viable and good sounding) and which extensions you cannot use most of the time. There’s only one “rule” for this and it’s the “b9 rule”. In short: we want to avoid having the interval of a b9 within a chord…
…and usually, that “b9” is created by the fact of adding one or many extensions! (-:
So the rule is: if this-or-that extension creates a b9 DON’T use it. (Only exception: between the root and the b9 of dominant chords.)
Of course, this has to be done “case by case”. We cannot assume that all minor 7th chords will “accept” the same extensions… we have to think in terms of function. For instance: “In the progression, is this min7 chord functionning as IIm7 or VIm7 ?” The answer will give you what SCALE is typically used for that function (and the origins of the chord at hand)… and then allow you to add 9, 11 and 13 on top.
Depending on the scale at issue, some extensions will “create” our #1 public ennemy, the b9 interval. This will bring you to understand exactly how to add jazz chord extensions (what, where and how.)
Truth be told, after you do this once for a certain chord function, you’re set! You’ll find the stuff that is commonplace and all the other stuff that is usually avoided.
Let’s do it!
Ok, so here it is! It’s going to be a bit more involved on the jazz theory side of building extensions so you’ll need a piece of paper and some time to puzzle things out for yourself.
- Write the scale down (two octaves);
- Define the 7th chord;
- Define the 9, 11 and 13 extensions;
- Determine wich of the three above are available according to the “b9 Rule”;
- Rinse and repeat.
Last step refers to using the next mode available, for example. If you just found the available extensions on a C major chord in the key of major, why not use the same process from D to D and find the available extensions on the IIm7 (Dm7) chord in the key of C major, etc.
An Example: the C major 7th chord in the key of C major
To get you started in jazz chord extensions, here’s an obvious example to demonstrate the “b9 rule” and the whole process… In fact, I’m asking myself the question: “What jazz chord extensions are available on a Cmaj7 chord in the key of C major?”
Step 1: Write the Scale Down
Step 2: Define the 7th Chord
Step 3: Write 9-11-13
Step 4: Apply the “b9 Rule”
So, what this process is telling us is that jazz chord extensions on C major 7th (acting like a I chord) are typically the 9th and the 13th (both natural). The natural 11th is usually avoided because the b9 it create with the 3rd. Voila! So “Cmaj9” or “Cmaj9(add 13)” or “C6/9” are commonplace while Cmaj11 is almost never encountered.
If you’re even mildly interest by this idea, I encourage you (very much!) to take 15 minutes and do this starting from all the notes in C major. You’ll be finding the “right” extensions for Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7(b5) in a C major tonality. It’s worth your while, I promise.
Then of course, replicate the exact same process with C melodic and C harmonic minor … you’ll find funny jazz chord extensions in funny places! (-:
Don’t forget to “relativize” the degree numbers. For instance, Dm7 in C major (dorian mode) is 1 b3 5 b7 9 11 13 … always use proper degrees… you’ll find beautifl extensions such as #11 and b13 !
What to do next?
This jazz theory idea can also be used in finding proper (allowed) extensions for secondary dominants chords, but this is beyond the scope of the article. For instance, what extensions are you allowed to add to an A7, D7 or E7 chord when the “key of the moment” is C major? These three chords are non-diatonic, so there’s some thinking to be done!