C9b5 guitar chord
An open string left ringing against a fretted grip. Because it costs no finger, it sounds a note the closed shape has none left for -- a tension on top, or a pedal root underneath. Either a familiar grip with open strings added, or a shape so sparse the open strings carry the chord. These belong to their key rather than to a shape, so D, A, G and E have many and Eb a handful.
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About C9b5 — open string voicings
C9b5 is C, E, Gb, Bb and D — C7b5 with the natural ninth added over it.
It sounds sleek and tense. Played as a tritone substitution the ♭5 is the root of the dominant it replaced.
C9b5 notes and formula
| C | E | Gb | Bb | D |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
Altered dominant — commonly the tritone substitute.
Also written C9(b5), C9-5 or C9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play C9b5
An open string left ringing against a fretted grip. It costs no finger, so it can sound a note the closed shape has none left for: a tension on top, or a pedal root underneath.
These belong to their key rather than to a shape: they cannot be moved up the neck. D, A, G and E have many; E♭ has a handful.
C9b5 has 2 of them, only on strings 6-5-4-3-2-1, from the 2nd fret up to the 4th — all in one inversion, so the bass note never moves. The one to learn first is the E shape at the 2nd fret.
Start with 8-9-8-9-x-10 — no barre. 1 of the 6 shapes here sits in open position. 4 of the 6 need a barre. Together they cover the neck from the 2nd fret to the 15th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x32332 | 2nd fret | C, root position | Gb | barred |
| x34330 | open position | C, root position | E | barred |
| 878778 | 7th fret | C, root position | C | barred |
| 8-9-8-9-x-10 | 8th fret | C, root position | D | all fretted |
| x-9-10-9-11-10 | 9th fret | Gb, 2nd inversion | D | all fretted |
| x-15-14-15-15-14 | 14th fret | C, root position | Gb | barred |
The same notes rebuilt from scratch give 9 shell and 13 rootless voicings, each on its own page.
Tensions. A shell of C9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (Ab) and the 13 (A).
How to use C9b5
C9b5 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, C9b5 → F. 3 voices move by a semitone, and one note is common to both chords.
| In C9b5 | Moves | In F |
|---|---|---|
| C, the root | stays where it is | C, the fifth |
| E, the major third | rises a semitone | F, the root |
| Gb, the flat fifth | falls a semitone | F, the root |
| Bb, the flat seventh | falls a semitone | A, the major third |
| D, the ninth | falls a whole tone | C, the fifth |
What to play over C9b5
Every note of C9b5 is in C whole tone and C lydian dominant.
Chords near C9b5
Change one note of C9b5 and you have C7b5 (drop the ninth), C9 (the flat fifth becomes a fifth), Caug9 (the flat fifth becomes a sharp fifth) or C9#11 (add the fifth).
C9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On C9b5’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.