A#9 Chord on Guitar
A#9 = A# – D – F – G# – C (Root, Major 3rd, Perfect 5th, Minor 7th, Major 9th)
A#9, more commonly written Bb9, is a dominant chord that piles a ninth on top of a full dominant seventh, fretted at the sixth-fret barre position. Like every dominant-ninth shape on this neck, the guitar voicing quietly drops the fifth, since a genuine five-note chord has no clean way to fit across six strings without doubling something.
In full, the chord is A#, D, F, G#, C — root, major third, fifth, flat seventh, ninth. As V9 it resolves toward D#/Eb major, and that pull is driven by the same mechanism as every dominant ninth: the major third wanting to rise a half step into the destination's root, and the flat seventh and ninth both wanting to fall. Because D#/Eb major isn't among the guitar's easiest open-position keys, A#9 shows up less in casual strumming than its A9 cousin does for D major, but it's a staple wherever horn-influenced soul, funk, or R&B material sits in flat keys.
Fingerings
Barre (6th fret)
How to Practice It
Run A# major into A#7 into A#9 in sequence and listen for how each version adds more forward pull toward the Eb resolution — that's a useful way to isolate exactly what the ninth contributes on top of the plain dominant seventh. Since the barre position matches plain A#/Bb major, this is good practice for adding extra fretted notes cleanly without disturbing the barre finger underneath.
Common Progressions
- A#9 – D# (V9 – I in Eb major)
- D# – A#9 – D# (I – V9 – I)
- Cm – A#9 – D# (ii – V9 – I in Eb major)
- A#9 – D# – G# – D# (V9 – I – IV – I)
FAQ
- What notes are in A#9/Bb9?
- A#, D, F, G#, and C fill out the full chord — root, major third, fifth, flat seventh, ninth — but a six-string hand leaves the fifth off the fretboard, since it's the tone the chord can most afford to lose.
- How does A#9 differ from A# add9?
- A#9 includes the flat seventh alongside the ninth, giving it a dominant, tension-carrying character, while A# add9 keeps a plain major triad and simply layers the ninth on top with no seventh at all.
- What key does A#9 pull toward?
- Eb (D#) major, since A#/Bb is the fifth degree of that key and this voicing carries the full dominant-ninth push toward it.
- Why is A#9 less commonly strummed than A9?
- Eb major isn't an easy open-position guitar key the way D major is, so material that resolves this chord toward Eb tends to come from horn-influenced or keyboard-first genres rather than simple acoustic songwriting.
- Is A#9 hard to finger compared to plain A#7?
- It asks for one additional stretch beyond the A#7 barre at the same position, a modest but real step up in difficulty.
- Does A#9 always need to resolve to Eb?
- Not strictly — like any dominant chord, it can function as a static, groove-based color in funk or soul writing that never actually resolves, treating the tension itself as the target sound.
- Why is the fifth dropped from this voicing?
- The fifth is the least essential tone for identifying a dominant chord's quality, so guitarists routinely leave it out in favor of keeping the root, third, seventh, and ninth intact within a six-string reach.
- Can A#9 substitute for a plain A#7 in a chart?
- Often yes, especially in a smoother, jazzier arrangement — the added ninth doesn't remove any of A#7's dominant function, it just enriches the color on top of it.
- Is there an easier way to reach A#9 lower on the neck?
- An A-shape barre near the first fret can approximate it, though dominant ninth chords get considerably more cramped in that shape, so most guitarists stick with the sixth-fret E-shape voicing used here for reliability.
- Does A#9 relate to G9 the way A#6 relates to Gm7?
- No — that shared-note trick is specific to sixth chords and their relative minor sevenths; A#9 is its own dominant sound with the ninth stacked over a full A#7, unrelated in construction to G9.
- What happens if the ninth is dropped from this voicing?
- The chord collapses back into plain A#7, still a strong dominant pulling toward Eb, just without the extra brightness the ninth was contributing on top.
- Why do dominant ninth chords sound jazzier than plain dominant sevenths?
- The extra ninth fills in more of the chord's upper harmonic space with closely related tones, giving the ear more to parse and evoking the denser voicings jazz pianists and guitarists have always favored.
- Is it common to alter the ninth in more adventurous jazz voicings?
- Yes — a sharp or flat ninth is a jazz-harmony staple for adding extra bite to a dominant chord, though the plain, unaltered ninth used here is the more foundational, widely applicable version.
A#9 on other instruments: A#9 on Piano. Related: how chords are built, chord finder.