A#9

Q: What notes are in the A#9 chord?

The A#9 chord (A# 9th) contains: A#, D, E#, G#, B#. Its interval structure is shown above in the Theory section.

Q: How do I build A#9 on the keyboard?

Take the root and add the remaining chord tones following the interval formula. The highlight shows chord content, while the inversion control changes which chord tone is in the bass.

Q: Which keys is A#9 found in?

The chord acts as a diatonic degree in several keys — they are marked on the circle of fifths in the "Harmonic context" block.

Q: What can I substitute for A#9?

A substitution depends on harmonic function and voice leading, not only on shared tones. Computed options appear in the "Substitutions" block and should be checked in context.

A# 9th

Octaves

Musical context

ChordA# majorTriad

ChordA#9A# 9th

ArpeggioA# majorBroken triad

ScaleA# major7 notes

KeyA# majorMajor key

ProgressionPop axisSequence

How the chord relates to the scale, mode, key and progression.

Theory

General info

Full name: A# 9th
Symbol: A#9
Root: A#
Quality: 9th

Chord notes

1A#root

3Dmajor 3rd

5E#perfect 5th

b7G#minor 7th

2B#major 2nd

Functions & resolutions

Typical function in key: VDominant (V)Eb major
Stability / tension: High tension — requires resolution
Most common resolutions: D#D# Major CmC Minor
Unstable degrees: 3D
4D#
resolves up to the resolution tonic
6G
b7G#
resolves down to the tonic 3rd
Main resolution: A#9source
D#D# Major
Dominant 7th A#7 naturally resolves up a 4th to D#. It is the tritone between the chord's 3rd and 7th that creates this pull.
Other resolutions: A#9source
Deceptive resolution
CmC Minor
Instead of the tonic, the dominant resolves to the vi degree. Creates surprise and is often used to extend a musical phrase.
A#9source
Modal resolution
G#G# Major
In rock and blues, the dominant often moves to bVII or IV instead of the tonic, creating a modal flavor.
A#9source
Jazz reharmonization
E7E Dominant 7
Tritone substitution: A#7 can be replaced by E7 (a tritone away). Both chords share the same tritone between the 3rd and 7th, resolving to the same tonic.
A#9source
Functional resolution
A#sus4A# Sus4
The dominant can resolve beyond the tonic: moving to IV (subdominant) or to a suspension (sus4) are common alternatives in pop and folk music.

Substitutions

Tritone substitution: E7E Dominant 7

Features

Character: Dominant, with a minor 7th and major 9th
Characteristic interval: 9th
Description: The major 3rd and minor 7th form a dominant core, while the major 9th adds a diatonic extension. The dominant tritone preserves directed tension toward resolution.
Application: V9–I in jazz
Funk and soul
Blues harmony

Voicing & structure

Root position

v1A#(A#4)Bass

root

v2D(D5)M3from A#

v3E#(E#5)m3from D

v4G#(G#5)m3from E#

v5B#(B#6)M3from G#

Harmony

Compatible scales

All chord tones are contained in these scales — use them for improvisation.

ScaleC Aeolian (natural minor)ScaleC Mixolydian ♭6 ScaleD Locrian ScaleD Altered (super Locrian)ScaleF Dorian ScaleF Melodic minor ScaleF Neapolitan major ScaleG# Lydian ScaleG# Lydian augmented ScaleA# Mixolydian

This chord on guitar 🎸

See how A#9 looks on guitar.

Explore

Circle of fifths

Highlighted major keys contain this chord among their diatonic harmonies.

Relative key: GmG minor
Dominant: FF major
Subdominant: EbEb major
Key signature: 2 flats (Bb, Eb)

What to learn next

ScaleBb MixolydianScale to improvise over this chord ChordA# Dominant 7A nearby chord on the same root — compare the sound PracticeChord trainerLock the fingering into muscle memory ProgressionChord progressionsHow this chord works inside real progressions ChordA# Major 9Another related chord to practise

Recommended for you

A# Dominant 7A chord that sounds close

A# Major 9A chord that sounds close

A# Minor 9A chord that sounds close

Bb MixolydianA scale related to this chord

Bb Chromatic scaleA scale related to this chord

Practice

Keyboard Trainer

Reinforce it in practice — play and name notes on the interactive keyboard.

Open Trainer

Test yourself

(Press any key to start)

What notes are in the A#9 chord?

How do I build A#9 on the keyboard?

Which keys is A#9 found in?

What can I substitute for A#9?

A#9