The A♯ Dominant 9th chord is a five-note chord made up of A♯, C♯♯, E♯, G♯, and B♯. It is built from a root, major third, perfect fifth, minor seventh, and major ninth.
Construction
A♯ Dominant 9th = Root + Major 3rd + Perfect 5th + Minor 7th + Major 2nd = A♯ · C♯♯ · E♯ · G♯ · B♯
| Note | Interval | Degree |
|---|---|---|
| A♯ | Root | 1 |
| C♯♯ | Major 3rd | 3 |
| E♯ | Perfect 5th | 5 |
| G♯ | Minor 7th | ♭7 |
| B♯ | Major 2nd | 9 |
Key Signature
A dominant chord points home to the key a fifth below its root: the A♯ Dominant 9th is the V (dominant) of D# Major, so the relevant key signature is that key’s — 3 flats (B♭, E♭, A♭). Spelled as a scale, these notes are A# Mixolydian.
B♭E♭A♭
Order of flats
Flats are added in a fixed order — the reverse of the sharp order. Each new flat key adds the next flat on the list.
B♭E♭A♭D♭G♭C♭F♭
Mnemonic: Battle Ends And Down Goes Charles’ Father
Chords in the Key of D♯ Major
These are the triads built on each degree of the D♯ major scale:
A♯ Dominant 9th — Frequently Asked Questions
What is the A♯ Dominant 9th chord on piano?
The A♯ Dominant 9th chord contains the notes A♯ – C♯♯ – E♯ – G♯ – B♯. On piano, play these notes together to sound the chord.
What notes are in the A# Dominant 9th chord?
The A# Dominant 9th chord (A#9) contains 5 notes: A#, D, F, G#, C. Formula: R-M3-P5-m7-M9.
How is A#9 used in music?
A#9 is used in jazz, fusion, and contemporary music to add harmonic color. It appears as a dominant or tonic chord depending on context.
What is the scale degree formula for A#9?
A#9 uses scale degrees 1-3-5-b7-9, giving it its distinctive sound.