Beyond the seventh: the stack keeps going
A seventh chord is built from stacked thirds: root, 3rd, 5th, 7th. Keep stacking and you reach the 9th (the 2nd, an octave up), the 11th (the 4th) and the 13th (the 6th). These are extensions. They colour the chord without changing its job.
Altered notes: more tension
On a dominant 7th chord (the V chord, which wants to resolve), you can raise or lower the 5th and 9th for extra tension. These are the altered notes: ♭9, ♯9, ♭5, ♯5 and ♭13. The more tension in the chord, the stronger the pull to resolve.
| Chord | Formula | Notes on C | Sounds |
|---|---|---|---|
| C7♭9dominant 7 flat 9 | 1 3 5 ♭7 ♭9 | C E G B♭ D♭ | dark, tense and a little exotic |
| C7♯9dominant 7 sharp 9 | 1 3 5 ♭7 ♯9 | C E G B♭ D♯ | gritty, bluesy and aggressive: the Hendrix chord |
| C7♭5dominant 7 flat 5 | 1 3 ♭5 ♭7 | C E G♭ B♭ | tense and jazzy, a tritone-flavoured dominant |
| C7♯11dominant 7 sharp 11 | 1 3 5 ♭7 ♯11 | C E G B♭ F♯ | bright, floating and dominant at once: the "Lydian dominant" |
| C13dominant 13th | 1 3 5 ♭7 9 13 | C E G B♭ D A | big, rich and swinging |
| C11dominant 11th | 1 3 5 ♭7 9 11 | C E G B♭ D F | open, suspended and funky: the 11th clashes with the third, so the third is usually left out |
| Cm11minor 11th | 1 ♭3 5 ♭7 9 11 | C E♭ G B♭ D F | deep, open and soulful |
| Cm13minor 13th | 1 ♭3 5 ♭7 9 13 | C E♭ G B♭ D A | warm, deep and open |
| Cmaj13major 13th | 1 3 5 7 9 13 | C E G B D A | wide, lush and glossy |
| Cmaj7♯11major 7 sharp 11 | 1 3 5 7 ♯11 | C E G B F♯ | dreamy and glittering: the Lydian tonic |
| C7altaltered dominant | 1 3 ♭7 ♯9 ♭13 | C E B♭ D♯ A♭ | maximum tension: every colour note altered |
Which one when?
- 7♭9: dark, "Spanish" tension. Standard before a minor chord (E7♭9 → Am).
- 7♯9: gritty and bluesy. Rock, funk and blues.
- 7♭5, 7♯11: jazz. The ♭5 and ♯11 are the same note, and both belong to the tritone-substitute sound.
- 13: big and swinging; a favourite final chord in jazz and blues.
- 11: the 11th (the 4th) clashes with the major third, so a dominant 11th usually leaves the third out and sounds like a suspended chord. Gospel and funk vamps.
- m11, m13: deep and modal, common in funk and neo-soul. The m13 adds a major 6th on top.
- maj13: a wide, lush tonic for jazz ballads.
- maj7♯11: the Lydian tonic: dreamy and bright.
- 7alt: maximum tension, nearly always resolving down a fifth.
Spelling matters
A ♯9 is spelled as a raised 9th (D♯ on a C7♯9), not as a ♭3 (E♭), even though they are the same key. The letter says what the note is doing in the chord. That is why enharmonic spelling matters.
How to practise
- Warm-up: 7, 9, 13 and m11 on white-key roots.
- Working set: the altered dominants on every root.
- Heavy lift: the full family including 7alt and 7♯5.
Learn the basics first with the sixth and ninth chords drill and the seventh chords drill, then see which scales fit with the chord-scale drill and the Extensions and Altered Dominants program.
Frequently asked questions
What is an altered chord?
A chord with one or more notes raised or lowered from the normal chord: usually a dominant 7th with a ♭9, ♯9, ♭5 or ♯5 (or ♭13). The changed notes add tension that wants to resolve.
What is a 7alt chord?
A dominant chord on which the 5th and 9th are altered, so every colour tone is a tense one. Players choose the altered scale (the 7th mode of melodic minor) over it. It almost always resolves to the I or i chord a fifth below.
What does the ♯ in 7♯11 mean?
The 11th is raised half a step, giving the Lydian dominant sound. A plain natural 11 clashes with the major third on a dominant chord, so the ♯11 is the usable version.
What is the difference between 13 and 6?
The 13th is the same note as the 6th, an octave higher. A "13 chord" is a seventh chord with the 9th and 13th stacked on top (C E G B♭ D A). A "6 chord" is just a triad plus the 6th and no seventh.
Do I have to play every note of a 13th chord?
No. Most 13th chords leave out the 5th and 11th. The 3rd, 7th and 13th define the sound.
Where is the Hendrix chord?
The 7♯9 chord (E7♯9 in Purple Haze) is nicknamed the Hendrix chord. Its ♯9 sits right next to the major 3rd and gives that bluesy clash.