C7b9 guitar chord
A close-position chord with the second voice from the top lowered an octave. Sits on four adjacent strings.
- Tap a note to hear it
- Arrows change position
- Fingers, notes or intervals
- Play the chord
About C7b9 — drop 2 voicings
C7b9 is C, E, G, Bb and Db — C9 with the ninth lowered a semitone.
It sounds dark and urgent. The flat ninth comes from the harmonic minor, so this is the V of a minor key rather than a major one.
C7b9 notes and formula
| C | E | G | Bb | Db |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♭9 |
Altered dominant — it points at a minor chord.
Also written C7(b9), C7-9 or C7♭9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play C7b9
Take the four notes stacked as close together as they go, then drop the second voice from the top an octave. The gap it opens is what makes the chord sound like a chord rather than a cluster.
It lands on four adjacent strings, which is why it is the workhorse voicing on guitar.
C7b9 has 13 of them, on the middle four strings, the bottom four strings and the top four strings, from the 2nd fret up to the 14th — every inversion the chord has: C in the bass, E in the bass, Bb in the bass and Db in the bass. The one to learn first is the C shape at the 2nd fret, which is the easiest grip here.
5 of them sit on the middle four strings, so you can run the inversions up one set without changing strings — which is the whole reason to learn them as a family rather than as separate grips.
Start with 8786xx — no barre. None of the shapes for C7b9 uses an open string, so every one of them is movable; the lowest sits at the 2nd fret. 3 of the 6 need a barre. Together they cover the neck from the 2nd fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x32323 | 2nd fret | C, root position | G | barred |
| 8786xx | 6th fret | C, root position | Db | all fretted |
| xx8989 | 8th fret | Bb, 3rd inversion | Db | all fretted |
| 8-10-8-9-8-9 | 8th fret | C, root position | Db | barred |
| x-x-10-9-11-9 | 9th fret | C, root position | Db | all fretted |
| x-15-14-15-14-15 | 14th fret | C, root position | G | barred |
The same notes rebuilt from scratch give 4 shell, 9 drop 3, 15 rootless and 1 open string voicings, each on its own page.
Tensions. A shell of C7b9, root, third and seventh, leaves a string free, and the tones that belong over it are the #11 (F#), the b13 (Ab) and the 13 (A).
How to use C7b9
C7b9 is a dominant with its tension raised, so it still points at F — harder than a plain seventh does, because the altered tones sit a semitone from where they are going.
Voice by voice, C7b9 → Fm. 3 voices move by a semitone, and one note is common to both chords.
| In C7b9 | Moves | In Fm |
|---|---|---|
| C, the root | stays where it is | C, the fifth |
| E, the major third | rises a semitone | F, the root |
| G, the fifth | rises a semitone | Ab, the minor third |
| Bb, the flat seventh | falls a whole tone | Ab, the minor third |
| Db, the flat ninth | falls a semitone | C, the fifth |
What to play over C7b9
Every note of C7b9 is in C half-whole diminished.
Chords near C7b9
Change one note of C7b9 and you have C7 (drop the flat ninth), C7/G (drop the flat ninth), Calt (the fifth becomes a sharp fifth), C9 (the flat ninth becomes a ninth) or C7#9 (the flat ninth becomes a minor third).
C7b9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On C7b9’s sound and use this page follows Mark Levine, The Jazz Theory Book (Sher Music, 1995). The shapes and the derived voicings come from different places, and both are explained in where the chords and the theory come from.