Extended chords go beyond the basic triad by adding more thirds on top — the 7th, 9th, 11th, and 13th. They're the source of the lush, complex sound in jazz, R&B, neo-soul, and modern pop.
Building Up From a Triad
Every extension adds another third above the previous note. Starting from C:
- Triad: C – E – G (root, 3rd, 5th)
- 7th chord: C – E – G – B (add the 7th)
- 9th chord: C – E – G – B – D (add the 9th, which is the 2nd up an octave)
- 11th chord: C – E – G – B – D – F (add the 11th)
- 13th chord: C – E – G – B – D – F – A (add the 13th)
In practice, you rarely voice all seven notes. Certain tones are omitted (usually the 5th and sometimes the root) to keep the chord playable and focused.
Seventh Chords
The 7th is the most common extension. The four main types:
| Name | Symbol | Formula | Sound |
|---|---|---|---|
| Major 7th | Cmaj7 | 1 – 3 – 5 – 7 | Dreamy, lush, resolved |
| Dominant 7th | C7 | 1 – 3 – 5 – ♭7 | Tense, bluesy, wants to resolve |
| Minor 7th | Cm7 | 1 – ♭3 – 5 – ♭7 | Smooth, melancholic, jazz |
| Half-diminished | Cm7♭5 | 1 – ♭3 – ♭5 – ♭7 | Dark, tense, unstable |
The dominant 7th (V7) is the most harmonically active — it intensifies the tension of the V chord and creates an even stronger pull toward I. In C major, G7 → C is one of the most satisfying moves in Western music.
Ninth Chords
Adding the 9th creates an airy, sophisticated quality popular in jazz and neo-soul:
- Major 9th (Cmaj9): 1 – 3 – 5 – 7 – 9 — very open and beautiful
- Dominant 9th (C9): 1 – 3 – 5 – ♭7 – 9 — funky, full of tension
- Minor 9th (Cm9): 1 – ♭3 – 5 – ♭7 – 9 — deeply emotional, R&B
Add Chords vs True Extensions
An add chord adds a note without including all the intermediate extensions. Cadd9 adds the 9th but does not include the 7th. This gives you the color of the 9th without the jazzy weight of the full 9th chord — common in pop and rock.
- Cadd9 = C – E – G – D (no 7th)
- Cmaj9 = C – E – G – B – D (includes 7th)
Suspended Chords
Suspended chords replace the 3rd with either the 2nd (sus2) or the 4th (sus4). They're neither major nor minor — they sound open and unresolved:
- Csus2: C – D – G
- Csus4: C – F – G
Sus4 chords are common in rock and pop guitar — they have a lifting, anticipatory quality that resolves naturally when the 4th drops to the 3rd.
Using Extensions in Songwriting
You don't need to use every note of an extended chord. Adding just the 7th or 9th to your basic triads is often enough to transform the emotional texture of a progression:
- Swap I (C) for Imaj7 (Cmaj7) for a dreamy, floating quality
- Use ii7 instead of ii for smoother jazz voice leading
- Add the 9th to a minor chord (Cm9) for a rich R&B feel
- Use a dominant 7th on V (G7) to make the resolution to I feel more inevitable