A#add9

Q: What notes are in the A#add9 chord?

The A#add9 chord (A# Add9) contains: A#, D, E#, B#. Its interval structure is shown above in the Theory section.

Q: How do I build A#add9 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#add9 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#add9?

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# Add9

Octaves

Musical context

ChordA# majorTriad

ChordA#add9A# Add9

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# Add9
Symbol: A#add9
Root: A#
Quality: Add9

Chord notes

1A#root

3Dmajor 3rd

5E#perfect 5th

2B#major 2nd

Functions & resolutions

Typical function in key: VDominant (V)Eb major
Stability / tension: Stable — can serve as major tonic
Most common resolutions: D#D# Major FF Major GmG Minor
Main resolution: A#add9source
FF Major
Major chord A# is a stable tonic. As tonic it doesn't require resolution, but in a progression context typically moves to IV or V.
Other resolutions: A#add9source
Deceptive resolution
GmG Minor
As the V degree, a major chord can defy expectations by moving to vi instead of I (deceptive cadence).
A#add9source
Modal resolution
G#G# Major
In modal context, a major chord can freely move to bVII, bIII, or bVI — characteristic of Mixolydian mode.
A#add9source
Jazz reharmonization
A#maj7A# Major 7
In jazz, a major chord is enriched to maj7, 6/9, or add9 and can smoothly transition into a ii-V of another key (modulation).
A#add9source
Functional resolution
FF Major
As the IV degree (subdominant), a major chord can resolve to V or directly to I (plagal cadence).

Features

Character: Major, with an added 9th and no 7th
Characteristic interval: 9th without 7th (add9)
Description: A major 9th is added to a major triad without a 7th. The chord retains a simple triadic core while adding second-based tension between root and 9th.
Application: Added-tone major tonic
Pop and rock
Arpeggiated textures

Voicing & structure

Root position

v1A#(A#4)Bass

root

v2D(D5)M3from A#

v3E#(E#5)m3from D

v4B#(B#6)P5from E#

Harmony

Compatible scales

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

ScaleF Yo (Japanese)ScaleA# Major pentatonic ScaleG Minor pentatonic ScaleG Blues scale ScaleC Dorian ScaleC Mixolydian ScaleC Aeolian (natural minor)ScaleC Mixolydian ♭6 ScaleD Phrygian ScaleD Aeolian (natural minor)

This chord on guitar 🎸

See how A#add9 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 Ionian (major)Scale to improvise over this chord PracticeChord trainerLock the fingering into muscle memory ProgressionChord progressionsHow this chord works inside real progressions

Recommended for you

Bb Ionian (major)A scale related to this chord

Bb LydianA scale related to this chord

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

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What notes are in the A#add9 chord?

How do I build A#add9 on the keyboard?

Which keys is A#add9 found in?

What can I substitute for A#add9?