Jazz Theory

Chords Construction – Part 2
Adding Extensions

On this page you’ll find some processes to build extensions on basic seventh chords (“jazz chords”). Some of the jazz theory concerns about seeing “9”, “11” and “13” besides chord symbols will be explained.

If you don’t read music (“notes” on the staff) and if you’ve never encountered any music theory in the past, this is a good place to start. Go slow, read on and don’t be afraid to ask questions!

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.

My goal here is to have you realize that you already know thousands of chords. (that is, if you already play a little bit) Why? Well, since any single chord can be put to use in many different contexts, it’s not a matter of learning more chords… it’s only a matter of finding more USES to the ones you already know! (-:

Jump to a page:

Chord Construction 1: Triads and Sevenths
Chord Construction 2: Adding Extensions [You’re Here]
Chord Construction 3: Equivalents
Chord Construction 4: Chords from three scales

Addendum: The “Chord Extensions Finder” Technique



  • Triads and Sevenths Chords have been covered in the previous installment of this jazz theory series.
  • The major scale still serves as reference for scale degrees…
    Degrees are raised by a sharp symbol (#) and lowered by the flat symbol (b).
  • When dealing with extensions…Extensions are (usually) identified as the notes 9, 11 and 13. It’s important to understand that 9=2, that 11=4 and that 13=6Because there’s only seven notes in the scale, the note “8” is in fact 1, the note “9” is in fact 2, the note “10”, etc.
  • You can think “linearly” : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (1)
    As in C D E F G A B C D E F G A B (C)
  • You can think “in thirds” : 1 3 5 7 9 11 13 (1)
    As in C E G B D F A (C)
  • Both ways to think are fine …


Building Extensions on the Guitar

So you’re seeing a chord on a chart that has 13, 11 or 9 (or all of them!) and you’re thinking “Easy! We had 1-3-5-7 now let’s just add 9-11-13 on top!” … right?! So the short answer is: ALMOST but not quite!

I believe that most of us wouldn’t want to deal with this jazz theory mess:

“If I want to build Cm(maj7)(b13) from scratch,
I need the notes … C-Eb-G-B-D-F-Ab … that’s: 1-b3-5-7-9-11-b13.”

Yuk! By the time you’re finished computing, the band is already playing the next tune in the book! So the lesson here is: we can’t go “blindly” and just build and build more notes above the root using thirds. Anyways, on the guitar we’re stuck with playing six notes at a time maximum! (-:

So, what’s the “jazz theory” solution? Well, most of the time, we wind up playing on parts of chords that have extensions. Very often, we omit the root and fifth of each chord (to make sure we play the important 3,7,9 etc.) Ideally, we just want to isolate the part of the chord we really need / want.

Of course, it’s best to understand the principles (that’s why you’re reading the jazz theory page, right?) So here’s my suggestion:


The First Trick

First, find the plainest 7th chord that is the closest to your “more complicated” chord with extensions. Then, change one (or a few) notes from the basic chord *TO* extensions.

chord-chart-3As an example let’s find a way to play “Cmaj7(13)”. The closest basic seventh chord is “Cmaj7”. Here are comfortable chord shapes for guitarists (pictured here.)

From this point, we are looking to get a “13”. Remember 13=6 so our “easiest” move here is to change the note “5” to a “6” within the original Cmaj7 and hear how it sounds. Can you identify the “fifth” in each shape?

Answer: for the two shapes on the top the “5” is the second lowest note, and the two bottom shapes it’s the highest note. What you want to do is take that note and raise it up to a “6”, that is TWO frets. In short: change the “G” note to an “A” note. I’ll leave you to enjoy discovering the new shapes… some may be comfortable and “playable” and some not! (-:

Basically, this process in jazz theory can be generalized by “moves”: you can take the basic notes 1-3-5-7 and move them up or down to an extension to experiment.Always let your ears be the final judge. Some stuff you’ll discover WON’T sound good at all! Here are movements that are legit for this:

1 to 9
3 to 11
5 to 13
5 to 11
7 to 13
You can also go to b9, #9, #11, b13 (etc.) with this same idea.

Of course, you may decide (or have to) change more than one note in a basic shape. Simply keep in mind that the root (1) and the fifth (5) are usually the first ones you want to sacrifice, and the 3 and 7 are (mostly) good to keep inside of the new chord. It’s not mandatory, just very common. Also: if you wind up changing 3-4 notes in your original chord, you’ll simply be playing a different chord altogether! It’s good to look at chord equivalents (next installment) to make your life easier…

Remember: any chord shape you currently know well (even if it’s NOT a basic 7th chord) can be used in this process. Change one or two notes and BINGO! you may find nice extensions. (For instance, C9 becomes C7(b9) or C7(#9) easily).


Getting Extensions by Changing the Voicing

Here’s anoter (more practical) idea: sometimes you cannot just change notes by using 1 to 9, 3 to 11, or 5 to13 … you have to be clever and re-voice the chord completely. That is, two notes (or more) can switch places so on top of creating extensions in a common shape, you’re completely changing the way the chord is voiced.

I’ll demonstrate with a favorite example of mine, so grab you guitar.

Our goal is to come up with a Cmaj9 voicing starting from this familiar shape: x3545x. I tried to move the root (1) up to 9 or the 3 down to 9 and I don’t really like the sound… so I’m gonna “hack my way” to the new extended chord like this: 3 to 9 and 5 to 3.

… basically, I’m “replacing” the 3 that I left out in the first move. In guitar fingers it gives us that x3545x has now become x3243x. Nice eh?! We can use the same jazz theory methodology starting from the familiar Cmaj7 in this shape: 8x998x Same process gives us… (hang on!) … 8x975x. See this:


Try and come up with new shapes using this litte jazz theory trick above (on your own this time!) Self-discovery is very powerful. More powerful in fact than if I simply “gave out” to you all the nice chords with extensions. (-:

Also, check out the article “Don’t Play That Chord” on JazzGuitarLessons.net here for more ideas on transforming some basic 7th chords into beautiful (useable) voicings.


Simplifying your life

As I mentionned early, it’s often easier to check out the jazz theory chords equivalents instead of changing all of the notes within a simple 7th chord. And that’s exactly what we’ll do in the next installment.


Jump to a page:

Chord Construction 1: Triads and Sevenths
Chord Construction 2: Adding Extensions [You’re Here]
Chord Construction 3: Equivalents
Chord Construction 4: Chords from three scales

Addendum: The “Chord Extensions Finder” Technique

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