C Seventh Sharp Nine Chord (C7♯9)

1Composition: what it contains

C – E – G – B♭ – D♯

Symbol

C7♯9

Also written

C7♯9, C7(♯9), C7+9

Formula

1 3 5 ♭7 ♯9

2Appearance: diagrams and sound

On the guitar

On the ukulele

On the piano

On the staff

On bass and as an arpeggio

3Indications: what it is used for

Famous in rock, funk, blues-rock and soul as a tonic dominant chord with attitude, and in jazz as an altered V7 resolving to I or i. Its sharp ninth is enharmonic to the minor third, so it suits minor-pentatonic soloing over a dominant groove. In jazz, the altered scale or half-whole diminished scale fits over it. It frequently appears in blues and funk vamps and as the V chord in minor ii–V–i progressions.

4Dosage: how to practise it

On guitar, learn the classic shape rooted on the fifth string (root, 3, ♭7, ♯9) and practise funk rhythms at 90–120 BPM, muting between hits. On piano, play the left-hand voicing 3-♭7-♯9 and the right-hand altered voicings. Practise iiø7–V7♯9–im and a twelve-bar blues with every chord as 7♯9. Arpeggiate the chord. Five to ten minutes daily. On piano, practise comping with short, accented hits. Try improvising with the blues scale over a 7♯9 vamp, then with the altered scale, to hear both colours.

5Warnings and common mistakes

The sharp ninth is not a minor third: it sits above the major third, which must also be present. Do not confuse 7♯9 with m7, which has no major third. Avoid placing the ♯9 below the third in voicings, which turns the sound into a muddy minor chord. In a major ii–V–I, the sharp ninth may clash with a melody containing the natural ninth. The symbol '7+9' is ambiguous; prefer 7♯9.

6Interactions with chords, scales and keys

Inversions

• Inversion 1 · C7♯9/E · E – G – B♭ – D♯ – C Play
• Inversion 2 · C7♯9/G · G – B♭ – D♯ – C – E Play
• Inversion 3 · C7♯9/B♭ · B♭ – D♯ – C – E – G Play
• Inversion 4 · C7♯9/D♯ · D♯ – C – E – G – B♭ Play

Scales to play over C7♯9

• C Half-Whole Diminished Scale

7Other presentations available

The same chord from every note

C♯7♯9 D7♯9 E♭7♯9 E7♯9 F7♯9 F♯7♯9 G7♯9 A♭7♯9 A7♯9 B♭7♯9 B7♯9

Other chords on C

C Cm Cdim Caug Csus2 Csus4 C5 C6 Cm6 C7 Cmaj7 Cm7 Cm7♭5 Cdim7 Cm(maj7) C7sus4 Cadd9 Cm(add9) C6/9 C9 Cmaj9 Cm9 C11 Cm11 C13 C7♭9 C7♯5 C7♭5