Bb+7(#9) Augmented
The Bb+7(#9) chord is built from the notes Bb – D – F# – Ab – C#.
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Also known as
Bb+7#9Bb7#5#9Bb7#9#5Bb7#9add#5Bb7(#5#9)Bb7+#9Bbaug7#9Bbaug7(no5)#9
Chord tones, one by one
BbRoot
Root
The fundamental note the chord is built on — Bb.
DThird
Major third
Four semitones — makes the chord major (brighter, happier).
F#Fifth
Augmented fifth (♯5)
Eight semitones — a sharp fifth. Restless and dreamy, typical of augmented chords.
AbSeventh
Minor seventh (♭7)
Ten semitones — the dominant/minor seventh. Adds bluesy tension (7, m7).
C#Extension
Sharp ninth (♯9)
A ♯9 — the gritty 'Hendrix' tension over a dominant chord.
🎼 Related scales
Altered (super-Locrian)melodic minor a semitone above
🎹 Modal analysis
This chord implies the Altered (super-Locrian) scale; its characteristic note is the ♭13, a dominant's maximum tension. It is a mode of the melodic minor a semitone above.
🎸 Genres
Modern jazz · Post-bop · Fusion