Extended chords are built by stacking 3rds above a triad: adding the 7th gives a 7th chord, adding the 9th gives a 9th chord, adding the 11th gives an 11th chord and adding the 13th gives a 13th chord. A C13 chord is C, E, G, Bb, D, F and A, built from the C major scale.
What are extended chords?
Extended chords are chords with five or more notes, built by continuing the same stacking pattern that makes a triad. A triad stacks two 3rds; a 7th chord stacks three; a 9th chord stacks four; an 11th chord stacks five; and a 13th chord stacks six, using every note of the scale. A C13 chord is C, E, G, Bb, D, F and A: the root, 3rd, 5th, 7th, 9th, 11th and 13th, which is every note of the C major scale except that the 7th is flattened, because a 13th chord is built on a dominant 7th. Extended chords are the harmonic language of jazz, and they appear in soul, R&B, funk and sophisticated pop as well. They sound richer and more complex than triads because each added note brings a new colour: the 9th adds sweetness, the 11th adds a floating, open quality, and the 13th adds warmth. The trade-off is that extended chords are harder to play and harder to voice well, since seven notes will not fit under four fingers, so players learn which notes to keep and which to leave out.
How extended chords are built
The method is always the same: keep stacking 3rds. Start with the chord's scale, take the odd-numbered degrees, and keep going. For a dominant 9th chord in C, take the 1st, 3rd, 5th, 7th and 9th degrees of the C mixolydian scale (C, D, E, F, G, A, Bb): C, E, G, Bb and D, which is C9. For a major 9th, use the major scale instead: C, E, G, B and D is Cmaj9. The quality of the 7th decides the family: a minor 7th gives dominant extensions, a major 7th gives major extensions, and a minor triad with a minor 7th gives minor extensions such as Cm9, C, Eb, G, Bb and D. The 11th and 13th need care because they can clash with the 3rd. In a C11 chord the 11th is F, which sits a semitone above the 3rd, E, so the two notes rub against each other. Jazz players solve this by leaving the 3rd out of 11th chords, or by raising the 11th to F#. In a C13 chord the 13th is A, which is a major 6th above the root, and it sounds warm and stable, so 13th chords are easier to use than 11th chords. On guitar the C9 guitar chord and the C13 guitar chord show how the shapes leave notes out, and the C major scale shows where the extensions come from.
Worked example — G13. Build it from the G mixolydian scale: G, A, B, C, D, E, F. Take the odd degrees: G (1st), B (3rd), D (5th), F (7th), A (9th), C (11th), E (13th). The full chord is G, B, D, F, A, C and E, but no guitarist plays all seven notes: a typical voicing keeps G, F, A and E, the root, 7th, 9th and 13th, and drops the 5th and 11th. The G13 guitar chord shows a practical voicing, and the G7 guitar chord is the triad-plus-7th underneath it. The chord finder builds any extended chord from any root.
How to practise extended chords
Learn extended chords one extension at a time, starting from the 7th chord you already know, and add the new note only when the smaller chord is comfortable.
- Play C7, then C9, then C13, adding one note at a time and listening to how each extension changes the colour.
- On guitar, learn the C9 guitar chord shape, then find the same chord with the 9th on a different string.
- On piano, play a dominant 7th chord with your left hand and add the 9th with your right hand, then the 13th, keeping the 3rd and 7th in the left hand.
- Play the ii–V–I progression in C major with 9th chords: Dm9, G9 and Cmaj9, and hear how much richer it sounds than the triad version.
- Use the scale finder to check which scale the extensions of a chord come from before you improvise over it.
Common mistakes
- Adding extensions to the wrong chord quality — A 9th chord built on a major triad with a minor 7th is a dominant 9th; the same notes with a major 7th are a major 9th. The 7th decides the family, so check it first.
- Playing all seven notes of a 13th chord — Seven notes at once sound muddy, especially in the low register. Keep the root, 3rd, 7th and the highest extension, and leave out the 5th and usually the 11th.
- Keeping the 3rd in an 11th chord — The 11th sits a semitone above the 3rd and the two clash badly. Leave the 3rd out of 11th chords, or raise the 11th to a sharp 11th, which is a favourite jazz sound.
Quick reference
Extended chords look complicated until you see them as a triad with extra layers, and this table breaks six common extensions down into exactly those layers. Each row starts from a triad, adds the 7th, and then adds the extension, so you can trace every note back to the stacking pattern that built it.
| Chord | Notes | How it is built |
|---|---|---|
| C9 | C – E – G – A# – D | Major triad + minor 7th + 9th |
| Cmaj9 | C – E – G – B – D | Major triad + major 7th + 9th |
| Cm9 | C – D# – G – A# – D | Minor triad + minor 7th + 9th |
| C13 | C – E – G – A# – D – F – A | Dominant 7th + 9th + 11th + 13th |
| G9 | G – B – D – F – A | Major triad + minor 7th + 9th |
| Am9 | A – C – E – G – B | Minor triad + minor 7th + 9th |
Practise the table by building each chord from the bottom up, adding one note at a time and naming it as you go: triad, 7th, extension. When you can build a 9th chord on any root by stacking 3rds, the 11th and 13th chords follow the same rule, and no extended chord will look intimidating again.
Frequently asked questions
What is an extended chord?
A chord with five or more notes, made by stacking 3rds above a triad. A 9th chord adds the 9th to a 7th chord, an 11th chord adds the 11th, and a 13th chord adds the 13th. The extensions come from the scale above the chord's octave.
How is a 9th chord different from an add9 chord?
A 9th chord contains the 7th as well as the 9th, while an add9 chord adds the 9th to a plain triad with no 7th. C9 is C, E, G, Bb and D; Cadd9 is C, E, G and D. The 7th is what makes it a true 9th chord.
Do I need to play every note of an extended chord?
No. In practice, extended chords are almost always played with notes left out, usually the 5th first. The root, 3rd, 7th and the highest extension are the essential notes; the rest add fullness but not identity.
Which extensions are safe for beginners?
The 9th is the safest and the most useful: it adds sweetness without clashing. The 13th is also friendly. The 11th is the trickiest because it clashes with the 3rd, so leave the 3rd out when you use it.
Where are extended chords used most?
In jazz, where they are the basic harmonic vocabulary, and in soul, R&B, funk and bossa nova. They appear in pop too, usually as 9th chords, which add richness without sounding complicated.