Bo9(#11) Diminished
The Bo9(#11) chord is built from the notes B – D – F – Ab – C# – E#.
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Chord tones, one by one
BRoot
Root
The fundamental note the chord is built on — B.
DThird
Minor third
Three semitones — makes the chord minor (darker, sadder).
FFifth
Diminished fifth (♭5)
Six semitones — a flat fifth. Creates instability, typical of m7♭5 and diminished chords.
AbSeventh
Diminished seventh (♭♭7)
Nine semitones — a doubly-flat seventh, found in fully diminished 7th chords.
C#Extension
Ninth (9)
A 9th — colorful extension a whole step above the octave.
E#Extension
Sharp eleventh (♯11)
A ♯11 — the bright, floating Lydian color.
🎼 Related scales
🎹 Modal analysis
This chord implies the Whole-half diminished scale.
🎸 Genres
Bebop jazz · Hard bop · Gypsy jazz