C#9b5 guitar chord
Root, third and seventh: the guide tones fix the quality, so the fifth is dropped. That is what leaves a string free, so pick a tension to put on top.
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About C#9b5 — shell voicings
C#9b5 is C#, E#, G, B and D# — C#7b5 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.
C#9b5 notes and formula
| C# | E# | G | B | D# |
|---|---|---|---|---|
| 1 | 3 | ♭5 | ♭7 | 9 |
Altered dominant — commonly the tritone substitute.
Also written C#9(b5), C#9-5 or C#9♭5. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play C#9b5
Root, third and seventh. The third and seventh, the guide tones, are what make the chord major, minor or dominant, so the fifth can go: it says nothing the symbol needs.
Three notes means a spare string, which is the real point. Put a tension on it.
C#9b5 has 8 of them, on the middle four strings, the bottom four strings, the top four strings, strings 5-3-2-1 and strings 6-4-3-2, from the 3rd fret up to the 10th — all in one inversion, so the bass note never moves. The one to learn first is the C# shape at the 3rd fret, which is the easiest grip here.
Start with 9-10-x-10-0-11 — no barre and 1 open string. None of the shapes for C#9b5 uses an open string, so every one of them is movable; the lowest sits at the 3rd fret. 2 of the 5 need a barre. Together they cover the neck from the 3rd fret to the 12th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x43443 | 3rd fret | C#, root position | G | barred |
| 989889 | 8th fret | C#, root position | C# | barred |
| 9-10-x-10-0-11 | 9th fret | C#, root position | D# | 1 open string |
| 9-10-9-10-x-11 | 9th fret | C#, root position | D# | all fretted |
| x-10-11-10-12-11 | 10th fret | G, 2nd inversion | D# | all fretted |
The same notes rebuilt from scratch give 13 rootless voicings, each on its own page.
Tensions. A shell of C#9b5, root, third and seventh, leaves a string free, and the tones that belong over it are the b13 (A) and the 13 (A#).
How to use C#9b5
C#9b5 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, C#9b5 → F#. 3 voices move by a semitone, and one note is common to both chords.
| In C#9b5 | Moves | In F# |
|---|---|---|
| C#, the root | stays where it is | C#, the fifth |
| E#, the major third | rises a semitone | F#, the root |
| G, the flat fifth | falls a semitone | F#, the root |
| B, the flat seventh | falls a semitone | A#, the major third |
| D#, the ninth | falls a whole tone | C#, the fifth |
What to play over C#9b5
Every note of C#9b5 is in C# whole tone and C# lydian dominant.
Chords near C#9b5
Change one note of C#9b5 and you have C#7b5 (drop the ninth), C#9 (the flat fifth becomes a fifth), C#aug9 (the flat fifth becomes a sharp fifth) or C#9#11 (add the fifth).
C#9b5 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On C#9b5’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.