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 Db Major, so the relevant key signature is that key’s — 5 flats (B♭, E♭, A♭, D♭, G♭). Spelled as a scale, these notes are Ab Mixolydian.
B♭E♭A♭D♭G♭
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 Ab Dominant 9th chord?
The Ab Dominant 9th chord (Ab9) contains 5 notes: Ab, C, Eb, Gb, Bb. Formula: R-M3-P5-m7-M9.
How is Ab9 used in music?
Ab9 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 Ab9?
Ab9 uses scale degrees 1-3-5-b7-9, giving it its distinctive sound.