A13#9 Dominant 7th
The A13#9 chord is built from the notes A – C# – E – G – B# – F#.
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Also known as
A13(#9)A7(#913)
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).
B#Extension
Sharp ninth (♯9)
A ♯9 — the gritty 'Hendrix' tension over a dominant chord.
F#Extension
Thirteenth (13)
A 13th — full, rich top extension.
🎼 Related scales
🎹 Modal analysis
This chord implies the Half-whole diminished scale; its characteristic note is the ♭9 / ♭2.
🎸 Genres
Bebop jazz · Hard bop · Gypsy jazz