Bb7#9 Bb dominant seventh sharp nine chord
- Notes
- Bb D F Ab C#
- Formula
- 1 3 5 b7 #9
- Semitones
- 0 4 7 10 15 above the root
- Also written
- A#7#9 (A# C## E# G# B##)
- Other symbols
- Bb7(#9), Bb7+9
Bb to D is a major third (4 semitones), D to F is a minor third (3 semitones), F to Ab is a minor third (3 semitones), Ab to C# is a perfect fourth (5 semitones). A dominant seventh with a raised ninth, C#. On the keyboard C# is the same key as the minor third, so the chord holds both a major and a minor third; it is written as a sharp ninth because it sits above the seventh and the letter names follow the stack of thirds.
Bb7#9 on the piano
Root position from Bb4: Bb4, D5, F5, Ab5, C#6. Middle C is C4.
Bb7#9 on the guitar
Standard tuning (E A D G B E). Strings run low E on the left to high e on the right, frets downwards; × is a muted string, ○ an open string, and each dot shows the note it sounds, with the root in blue-green. Every shape below has Bb as its lowest note.
x 1 0 1 2 x (low E to high e)
Sounds Bb2 D3 Ab3 C#4, fifth left out
The E-shape and A-shape grips are movable: an E-shape chord's root is the note under your first finger on the low E string, an A-shape chord's root is the note on the A string. Slide the same grip up or down to play dominant seventh sharp nine chords on other roots.
Inversions of Bb7#9
An inversion puts a note other than the root in the bass. The name is what semicord's chord finder calls those notes played bottom to top; a slash name like C/E means a C chord with E in the bass.
| Position | Notes, bass first | Named | Listen |
|---|---|---|---|
| Root position | Bb D F Ab C# | Bb7#9 | |
| 1st inversion | D F Ab C# Bb | Bbm7/D (also read as Bb7#9/D) | |
| 2nd inversion | F Ab C# Bb D | Bb7#9/F | |
| 3rd inversion | Ab C# Bb D F | Bb7#9/Ab | |
| 4th inversion | C# Bb D F Ab | Bb7/Db (also read as Bb7#9/C#) |
Where Bb7#9 fits
Bb7#9 has no place among the chords built from a major or minor scale: it holds a major third, D, and the sharp ninth C#, which sounds the same as the minor third. That major–minor clash is the blues in one chord. It is used as the I chord of a blues or a funk vamp, and as a tense V chord in jazz; Jimi Hendrix's "Purple Haze" made E7#9 famous, which is why guitarists call it the Hendrix chord.