A7#9

Q: What notes are in the A7#9 chord?

The A7#9 chord (A 7#9) contains: A, C#, E, G, B#. Its interval structure is shown above in the Theory section.

Q: How do I build A7#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 A7#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 A7#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 7#9

Octaves

Musical context

ChordA majorTriad

ChordA7#9A 7#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 7#9
Symbol: A7#9
Root: A
Quality: 7#9

Chord notes

1Aroot

3C#major 3rd

5Eperfect 5th

b7Gminor 7th

#2B#aug 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
6F#
b7G
resolves down to the tonic 3rd
#2C
4D
resolves to the resolution tonic
Main resolution: A7#9source
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: A7#9source
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.
A7#9source
Modal resolution
GG Major
In rock and blues, the dominant often moves to bVII or IV instead of the tonic, creating a modal flavor.
A7#9source
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.
A7#9source
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 an augmented 9th
Characteristic interval: Minor 7th (b7), Augmented 9th (#9)
Description: The augmented 9th is enharmonically equivalent to a minor 3rd and sounds alongside the chord’s major 3rd. Their chromatic clash creates sharp tension characteristic of blues and rock.
Application: Blues rock (Jimi Hendrix "Purple Haze")
Funk
Jazz fusion

Voicing & structure

Root position

v1A(A4)Bass

root

v2C#(C#5)M3from A

v3E(E5)m3from C#

v4G(G5)m3from E

v5B#(B#6)P4from G

Harmony

Compatible scales

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

ScaleC# Hungarian minor ScaleF Harmonic major ScaleG# Double harmonic ScaleG# Persian scale ScaleG# Byzantine ScaleC Diminished (half–whole)ScaleC# Diminished scale ScaleE Diminished scale ScaleE Bebop melodic minor ScaleG Diminished scale

This chord on guitar 🎸

See how A7#9 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 A7#9 chord?

How do I build A7#9 on the keyboard?

Which keys is A7#9 found in?

What can I substitute for A7#9?