Aaug9

Q: What notes are in the Aaug9 chord?

The Aaug9 chord (A Aug 9) contains: A, C#, E#, G, B. Its interval structure is shown above in the Theory section.

Q: How do I build Aaug9 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 Aaug9 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 Aaug9?

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

ChordAaugTriad

ChordAaug9A 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: Aaug9
Root: A
Quality: Aug 9

Chord notes

1Aroot

3C#major 3rd

#5E#aug 5th

b7Gminor 7th

2Bmajor 2nd

Functions & resolutions

Typical function in key: VDominant (V)D major
Stability / tension: High tension — requires resolution
Most common resolutions: DD Major BmB Minor
Unstable degrees: 3C#
4D
resolves up to the resolution tonic
#5F
6F#
resolves up to the tonic 3rd
6F#
b7G
resolves down to the tonic 3rd
Main resolution: Aaug9source
DD Major
Dominant 7th A7 naturally resolves up a 4th to D. It is the tritone between the chord's 3rd and 7th that creates this pull.
Other resolutions: Aaug9source
Deceptive resolution
BmB Minor
Instead of the tonic, the dominant resolves to the vi degree. Creates surprise and is often used to extend a musical phrase.
Aaug9source
Modal resolution
GG Major
In rock and blues, the dominant often moves to bVII or IV instead of the tonic, creating a modal flavor.
Aaug9source
Jazz reharmonization
D#7D# Dominant 7
Tritone substitution: A7 can be replaced by D#7 (a tritone away). Both chords share the same tritone between the 3rd and 7th, resolving to the same tonic.
Aaug9source
Functional resolution
Asus4A 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: Eb7Eb 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(A4)Bass

root

v2C#(C#5)M3from A

v3E#(E#5)M3from C#

v4G(G5)M2from E#

v5B(B5)M3from G

Harmony

Compatible scales

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

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

This chord on guitar 🎸

See how Aaug9 looks on guitar.

Explore

Circle of fifths

Highlighted major keys contain this chord among their diatonic harmonies.

Relative key: F#mF# minor
Dominant: EE major
Subdominant: DD major
Key signature: 3 sharps (F#, C#, G#)

What to learn next

ScaleA 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

A 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 Aaug9 chord?

How do I build Aaug9 on the keyboard?

Which keys is Aaug9 found in?

What can I substitute for Aaug9?