A13b9 Dominant 7th
The A13b9 chord is built from the notes A – C# – E – G – Bb – D – F#.
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Chord tones, one by one
ARoot
Root
The fundamental note the chord is built on — A.
C#Third
Major third
Four semitones — makes the chord major (brighter, happier).
EFifth
Perfect fifth
Seven semitones — the most stable interval, reinforces the root.
GSeventh
Minor seventh (♭7)
Ten semitones — the dominant/minor seventh. Adds bluesy tension (7, m7).
BbExtension
Flat ninth (♭9)
A ♭9 — sharp, dissonant tension typical of altered dominant chords.
DExtension
Eleventh (11)
An 11th — a suspended, airy color on top of the chord.
F#Extension
Thirteenth (13)
A 13th — full, rich top extension.
🎼 Related scales
Mixolydian ♭9harmonic major scale
🎹 Modal analysis
This chord implies the Mixolydian ♭9 scale; its characteristic note is the ♭9 / ♭2. It is a mode of the harmonic major scale.
🎸 Genres
Modern jazz · Post-bop · Fusion