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Chord Extensions Made Easy

Jordan Leibel  /  Chord Theory  /  UPDATED Jan 10, 2023

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Chord extensions are one of those things that sound intimidating. When someone says play a 9th or an 11th, what on earth does that mean?

Fortunately, once you understand the logic behind the numbers chord extensions become pretty simple.  Think about some of the simplest chords you know. You’re probably thinking of a C major triad or maybe a G major or something similar, right? I like to think of a chord extension as any note played in a chord that goes beyond the major or minor triad structure.  

Typically, most chords are built by stacking 3rds on top of each other. So if you think about those major triads, they contain a 1, a major 3rd, and a perfect 5th (which is really just a minor 3rd about the middle note in the chord).

What if you add another 3rd above the 5th? You’ll be playing the 1, 3, 5, and the 7th note of the scale. Depending on what kind of 3rd you add above the triad, you’ll create different a different kind of 7th chord.  

But what about those 9ths, 11ths or 13ths you may have heard about? They’re not so tough either. A major scale contains 8 notes (well technically 7 plus the octave, but you get the idea). But if you keep counting beyond the 1-octave, you’ll see that a 9th is really just the 2nd note of the scale played an octave higher, the 11th is just the 4th played an octave higher and the 13th is just a 6th played an octave higher.

So even though all those numbers seem intimidating, the logic of them is quite simple. Of course, voicing these extended chords is a deep rabbit hole, but if you’ve ever wondered about where they get those chord numbers from, now you know! 


Jordan Leibel is passionate about songwriting, improvisation, and helping you become a creative musician! He’s worked as a composer for film, commercial, and theatre projects as well as a session musician and producer for recording work.

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