A Dominant Sharp 9th
A7♯9
Notes
A · C♯ · E · G · B♯
Intervals
- RootA (1P)
- Major 3rdC♯ (3M)
- Perfect 5thE (5P)
- Minor 7thG (7m)
- Augmented 9thB♯ (9A)
Fretboard
On the fretboard, C represents B♯.
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About
The A7♯9 (A–C♯–E–G–B♯) raises the ninth a half step, creating a striking enharmonic clash: the B♯ (sounding like a ♭3) sits against the major 3rd in the same chord. This makes the chord simultaneously major and minor in feeling — the C♯ is in the bass of the voicing while the ♯9 rings on top like a minor color. The result is a harmonically ambiguous but intensely bluesy sound, which is why it is central to rock and blues-rock harmony — the "Hendrix chord". The 3rd and ♭7 are essential; the ♯9 is the defining alteration. Compared to A7♭9, 7♯9 feels more bluesy than classically tense.
Similar chords
Chords sharing two or more notes with this one, ranked by overlap.
Scales containing this chord
Scales whose notes include every chord tone. The Roman numeral (or scale degree) marks the chord root’s position in the scale.