A#aug9

Q: What notes are in the A#aug9 chord?

The A#aug9 chord (A# Aug 9) contains: A#, D, F#, G#, B#. Its interval structure is shown above in the Theory section.

Q: How do I build A#aug9 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#aug9 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#aug9?

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# Aug 9

Octaves

Musical context

ChordA#augTriad

ChordA#aug9A# Aug 9

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# Aug 9
Symbol: A#aug9
Root: A#
Quality: Aug 9

Chord notes

1A#root

3Dmajor 3rd

#5F#aug 5th

b7G#minor 7th

2B#major 2nd

Functions & resolutions

Stability / tension: High tension — requires resolution
Most common resolutions: D#D# Major CmC Minor
Unstable degrees: 3D
4D#
resolves up to the resolution tonic
#5F#
6G
resolves up to the tonic 3rd
6G
b7G#
resolves down to the tonic 3rd
Main resolution: A#aug9source
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#aug9source
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#aug9source
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#aug9source
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#aug9source
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 9th and augmented 5th
Characteristic interval: Augmented 5th (#5), 9th
Description: The augmented 5th destabilises the triadic core, the minor 7th preserves dominant function, and the major 9th extends the chord. The #5 alteration intensifies chromatic voice leading.
Application: V+ → I in jazz
Altered blues
Passing chords

Voicing & structure

Root position

v1A#(A#4)Bass

root

v2D(D5)M3from A#

v3F#(F#5)M3from D

v4G#(G#5)M2from F#

v5B#(B#6)M3from G#

Harmony

Compatible scales

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

ScaleC Whole tone scale ScaleD Whole tone scale ScaleF# Whole tone scale ScaleG# Whole tone scale ScaleA# Whole tone scale ScaleE Whole tone scale ScaleD Enigmatic scale ScaleD Altered (super Locrian)ScaleF# Lydian augmented ScaleA# Mixolydian ♭6

This chord on guitar 🎸

See how A#aug9 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 Chromatic scaleScale to improvise over this chord PracticeChord trainerLock the fingering into muscle memory ProgressionChord progressionsHow this chord works inside real progressions

Recommended for you

Bb Chromatic scaleA scale related to this chord

Practice

Keyboard Trainer

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

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Test yourself

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What notes are in the A#aug9 chord?

How do I build A#aug9 on the keyboard?

Which keys is A#aug9 found in?

What can I substitute for A#aug9?