C7#9 guitar chord
The third voice from the top lowered an octave. The dropped voice becomes the bass, which is why a string is skipped.
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About C7#9 — drop 3 voicings
C7#9 is C, E, G, Bb and D# — C9 with the ninth raised a semitone.
It sounds gritty and contradictory. The minor third sounding over the major third; every guitarist knows it as the Hendrix chord.
C7#9 notes and formula
| C | E | G | Bb | D# |
|---|---|---|---|---|
| 1 | 3 | 5 | ♭7 | ♯9 |
Altered dominant — dominant function with a blues third on top.
Also written C7(#9), C7+9 or C7♯9. The same chord either way; which spelling you meet depends on who wrote the chart.
How to play C7#9
The same operation one voice further down: the third voice from the top falls an octave and becomes the bass.
That leaves a bigger hole under the top three notes, so a string gets skipped: the muted string in the middle is the shape, not a mistake.
C7#9 has 9 of them, on strings 6-4-3-2 and strings 5-3-2-1, from open position up to the 12th — every inversion the chord has: C in the bass, E in the bass, Bb in the bass and D# in the bass. The one to learn first is the E shape at the nut.
5 of them sit on strings 6-4-3-2, 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 x3234x — no barre and down at the nut. 1 of the 9 shapes here sits in open position. 4 of the 9 need a barre. Together they cover the neck from the 2nd fret to the 11th.
| Frets | Where | Bass | Top | Hand |
|---|---|---|---|---|
| x3234x | 2nd fret | C, root position | D# | all fretted |
| x35340 | open position | C, root position | E | 1 open string |
| x65556 | 5th fret | D#, 9th in the bass | Bb | barred |
| 8788xx | 7th fret | C, root position | D# | barred |
| x78888 | 7th fret | E, 1st inversion | C | barred |
| 8-10-8-9-8-11 | 8th fret | C, root position | D# | barred |
| 8-10-8-9-11-11 | 8th fret | C, root position | D# | all fretted |
| x-x-10-9-11-11 | 9th fret | C, root position | D# | all fretted |
| x-10-10-9-11-11 | 9th fret | G, 2nd inversion | D# | all fretted |
The same notes rebuilt from scratch give 3 shell, 14 drop 2 and 12 rootless voicings, each on its own page.
Tensions. A shell of C7#9, 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 C7#9
C7#9 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, C7#9 → F. 2 voices move by a semitone, and one note is common to both chords.
| In C7#9 | 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 fifth | falls a whole tone | F, the root |
| Bb, the flat seventh | falls a semitone | A, the major third |
| D#, the sharp ninth | rises a whole tone | F, the root |
What to play over C7#9
Every note of C7#9 is in C half-whole diminished.
Chords near C7#9
Change one note of C7#9 and you have Cm7 (drop the major third), Cm9 (the major third becomes a ninth), C7 (drop the minor third), C7/G (drop the minor third), C9 (the minor third becomes a ninth) or C7b9 (the minor third becomes a flat ninth).
C7#9 is an altered chord — a dominant seventh with its fifth or ninth moved. Altered dominant chords on every root.
On C7#9’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.