Bb Half-diminished
Bbm7b5
Notes
Bb · Db · Fb · Ab
Intervals
- RootBb (1P)
- Minor 3rdDb (3m)
- Diminished 5thFb (5d)
- Minor 7thAb (7m)
Fretboard
On the fretboard, E represents Fb.
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About
The B♭ half-diminished (B♭–D♭–F♭–A♭), also written B♭ø7, is the naturally occurring chord on the seventh degree of a major scale and on the second degree of a natural minor scale. Its primary role in jazz is as the ii chord in a minor ii–V–i: B♭m7♭5 → E♭7 → A♭m. The F♭ is the defining color tone — without it, the chord collapses to a plain B♭m7. The 3rd and ♭7 together establish the minor seventh quality. On guitar, the fifth is essential and should not be omitted, since the ♭5 is precisely what distinguishes this chord. Compared to B♭dim7, m7♭5 is more grounded due to the natural (rather than doubly-flatted) seventh, giving it a somber but less frantic character.
Similar chords
Chords sharing two or more notes with this one, ranked by overlap.
Scales containing this chord
- B♭ Blues (deg 1)
- A♭ Diminished (deg 2)
- A♭ Harmonic Minor (II)
- A♭ Natural Minor (II)
- B Diminished (deg 8)
- B Major (VII)
- B Melodic Minor (VII)
- D Diminished (deg 6)
- D♭ Diminished (deg 6)
- D♭ Harmonic Minor (VI)
- D♭ Melodic Minor (VI)
- D♭ Natural Minor (VI)
- F Diminished (deg 4)
- F Harmonic Minor (IV)
- B♭ Locrian (I)
- A♭ Locrian (II)
- A♭ Phrygian (II)
- D♭ Dorian (VI)
- D♭ Locrian (VI)
- D♭ Phrygian (VI)
- E Lydian (IV)
- E♭ Locrian (V)
- E♭ Phrygian (V)
- F♯ Mixolydian (III)
Scales whose notes include every chord tone. Roman numeral marks the chord root’s position in the scale; dashed badges aren’t linked yet.