Jazz Chord Extensions

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.

Have fun! Jazz theory rules !


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.

This whole idea is something I picked from Michael Berard (my first “real” jazz guitar teacher) and his wonderful Jazz Guitar Elements book. Let’s do it…

  1. Write the scale down (two octaves);
  2. Define the 7th chord;
  3. Define the 9, 11 and 13 extensions;
  4. Determine wich of the three above are available according to the “b9 Rule”;
  5. 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

jazz theory rules

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?

jazz-chord-extensions in JG ElementsThis 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!

I encourage you to check out all the details in Jazz Guitar Elements by Michael Berard and build all the jazz chord extensions you can! (-:


11 thoughts on “Jazz Chord Extensions

  1. Hi! Thanks first. this is so helpful for me to explore the extension chord.
    Can the “b9 rule” apply to the altered note? such as “#9, “#11”
    So, for example, Cmaj in C key can use Cmaj7#9#11 since no b9 note exists.

    • Well, in a few words: no. The b9 rule is just a “rule of thumb”, and it doesn’t apply to altered chords. For instance, on G7b9 as a closed voicing (on piano) you have G-B-D-F-Ab … and there’s obviously a b9 interval in between the G and the Ab. But the chord is fully functional. The “b9 rule” is another way for us to say “watch out for the *avoid* note” and/or “careful with the tritone”. However, there’s plenty of example of major chords with b9 that can work in context. Cmaj7#9#11 doesn’t have a b9, and it works. However, check this Cmaj9 out: x79787 … one of my favorite voicings (ever) yet, we have a b9 interval! Long story shorts: learn the rules, then break them. 🙂

  2. What is this? D/F#. I was told that this was a chord extension, but I knew that that was not quite right. I’ll tell you what I think it means and you let me know if I am somewhere in the stellar neighborhood, okay? Thanks. I believe that chordally it could be written I/iii, meaning it’s a D major chord with F# in the bass, or simply, F# is the lowest note of the chord or 1rst inversion. Pleas get back to me when you can an let me know. Also what is that process called ( D/F#) when someone does this in a piece of music, this sort of fraction procedure? Thank you very much! Yours Tom

    • Hey Thomas. D/F# is first inversion D major triad. There are other instances where musician call this a “slash chord”, especially when the bass note (to the right of the slash) is not part of the chord (to the left of the slash). An example: D/F is a D major triad with a F note in the bass (yuck!). And it’s what we could call a slash chord. You can also do this with 7th chords: Cmaj7/E is a first inversion of Cmaj7 chord. Or even Cmaj7/A, where the A note in the bass is not part of Cmaj7. Lots of modern composers use these chords. 🙂 (Also see: upper structure triads)

  3. Hi! I’ve been working through Michael Berard’s book and have been stuck on this section for a while now. I understand the idea of the ‘b9 rule’ but when I work through the exercises and then check the answers I seem to be getting them wrong. Usually I find that I should have put b9 or b13 or a #11 instead of just a 9, 13 or 11. How do I know when the 9th, 11th, or 13th should be flattened or sharpened or just left natural? I’m not sure if i’m missing something or if this is just not covered in the book because it should already be understood? Any explanation or clarification would be very much appreciated. Cheers!!

  4. Hi Angie,

    First off, the b9 rule applies to constructing chords to find out which chord extensions are possible. This is to avoid using things like a b9 on a maj7 chord. Doesn’t sound good as an extension. The b9 interval is the most dissonant of intervals and when we hear it inside a chord voicing it overpowers the sound of the chord and we tend to hear it before anything else.

    Where and when to use which extensions on chords is a difficult topic for sure. When you are working through the exercises on finding extensions, you need to make sure you are writing each scale out correctly with all of the sharps and/or flats for that particular scale. As an example, let’s take C melodic minor. Make sure you only have an Eb on C melodic minor scale. For the third note in the scale (Eb) we will have an Ebmaj(#5) chord. Notes of the chord are: Eb G B D. (root, major 3rd, augmented 5th and major 7th) 9, 11 and 13 will be: F A and C which will be 9th (major) #11 and 13.

    Next check each of the 3 extensions for problematic b9 intervals. root – 9th (Eb to F an octave higher) creates the interval of a maj 9th so that’s good. The interval between the 3rd and the #11 (G to A an octave higher) also a major 9th and therefor good as well, from the #5 to the 13 (B to C an octave higher) generates the interval of a b9 and is therefor not an available extension. (do not use the 13th)

    Note. It is possible to use the 13th if you omit the #5.

    Also, keep in mind that this applies only to chord voicings and not improvisation. Of course you can still play all 7 notes of the scale in solos. A chord is a vertical representation of a scale and the scale itself is a horizontal representation. With a chord, all the notes are sounding at the same time vs a scale where we hear only one note at a time. Because of this, different rules apply.

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