Master the A# 7#9 Guitar Chord: Play & Get Feedback
A#7#9 (A# seventh sharp nine) follows the formula 1, 3, 5, b7, #9, so on A# it reads A#, C##, E#, G# and B##. It is a dominant seventh with one altered tone, the raised ninth B##, and it is often called the Hendrix chord.
There are three voicings listed for this root, and one of them uses an open string. Bb7#9 is its enharmonic twin, with the same pitches and different note names. The A# Half-Whole scale, the eight-note scale built from alternating half steps and whole steps, lines up with A#7#9, because it contains all five chord tones.
Hear A#7#9 as a strum and as an arpeggio on the interactive fretboard at the top, one string at a time.
A# 7th with sharp 9th guitar chord is also written as A#7(#9), A#7#9 or A#7+9. It is also known as the Hendrix chord.
A#7#9 Chord Notes and Formula
Notes in the A# 7(#9) chord:
Tones of the Dominant Seventh Sharp Ninth Added chord:
Formula: 1 3 5 b7 #9
Same chord, different name: A#7#9 is also written as Bb7#9 (Bb seventh sharp nine).
A# 7(#9) Chord Interactive Fretboard
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A# 7(#9) Guitar Chord Diagrams
Position 1 Open
Finger Positions
- Mute the low E string
- Let the D string play without pressing any fret
- Place your index finger (1) on the fret 1 of the A string
- Place your middle finger (2) on the fret 1 of the G string
- Place your ring finger (3) on the fret 1 of the high E string
- Place your pinky finger (4) on the fret 2 of the B string
Position 2 Barre Movable
Finger Positions
- Mute the high E string
- Place your index finger (1) on the fret 5 of the A string
- Place your middle finger (2) on the fret 6 of the low E string
- Place your ring finger (3) on the fret 6 of the D, G and B strings at the same time
Position 3 Barre Movable
Finger Positions
- Place your index finger (1) on the fret 6 of the low E, D and B strings at the same time
- Place your middle finger (2) on the fret 7 of the G string
- Place your ring finger (3) on the fret 8 of the A string
- Place your pinky finger (4) on the fret 9 of the high E string
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Chords That Go With A#7#9
One key where A#7#9 fits is Eb major, where it works as the V chord. These are the main chords of that key, the ones you will often hear around it:
See every key in the guitar keys chart, or build a progression with these chords in the chord progression generator.
More A# Chords
Want to know how this chord is built? Read dominant chords explained, or browse all A# guitar chords.
Created by
Giancarlo is a musician (teaching guitar since 2000), software engineer, AI consultant and published researcher
FAQ
Which notes are in the A# seventh sharp nine chord?
A#, C##, E#, G# and B##. The first four make an A# seventh chord, and B## is the sharp ninth. It sounds like C# but is named B## to keep the letters stacked in thirds.
Is A#7#9 the same as Bb7#9?
Yes, they sound identical. Bb7#9 is spelled Bb, D, F, Ab and C#, so it avoids double sharps, while A#7#9 uses A#, C##, E#, G# and B##. Both names point to the same pitches.
Why does A#7#9 need both C## and B##?
The third of the chord must use the letter C and the ninth the letter B. A major third from A# is C##, which sounds like D, and the sharp ninth is B##, which sounds like C#.
What scale fits A#7#9?
The A# Half-Whole scale: A#, B, B##, C##, D##, E#, F## and G#. It has eight notes built from alternating half and whole steps, and it contains all five chord tones.
How many voicings are listed for A#7#9?
Three voicings are listed, from the first fret up to the ninth fret. One of them uses open strings and two are barre voicings.
