Chords
Bb Half-diminished
Bb · Db · Fb · Ab
The half-diminished seventh — a diminished triad with a minor seventh. The ii of a minor key.
Also written Bbø · Bbø7 · Bb-7b5 · Bbh7 · Bbh
Bb Half-diminished
Bb · Db · Fb · Ab
Voicings on the piano
| Voicing | Notes | Play it on your instrument |
|---|---|---|
| Closed, root position | Bb3 · Db4 · Fb4 · Ab4 | |
| Open (drop 2) | Fb3 · Bb3 · Db4 · Ab4 | |
| Shell | Bb3 · Db4 · Ab4 | |
| Rootless | Db4 · Fb4 · Ab4 · Bb4 |
Tap a key or a fret to hear it.
Anatomy
Bb Half-diminished (Bbm7b5) contains the notes Bb · Db · Fb · Ab, each with a role measured as an interval from the root.
Read on: how triads are built · seventh chords
Inversions
An inversion of Bb Half-diminished puts a chord tone other than Bb in the bass; the name after the slash is that bass note.
Where it lives
The keys and the scales Bb Half-diminished belongs to.
In which keys
Bb Half-diminished is diatonic to 3 keys; the numeral is its degree and the label its harmonic function.
Scales that contain it
Bb Half-diminished fits inside these scales, each built on Bb.
- Bb Minor BluesBb · Db · Eb · Fb · F · Ab
- Bb LocrianBb · Cb · Db · Eb · Fb · Gb · Ab
- Bb AlteredBb · Cb · C# · D · E · Gb · Ab
- Bb Half-Whole DiminishedBb · Cb · Db · D · E · F · G · Ab
- Bb Locrian PentatonicBb · Db · Eb · Fb · Ab
- Bb Locrian #2Bb · C · Db · Eb · Fb · Gb · Ab
- Bb Locrian 6Bb · Cb · Db · Eb · Fb · G · Ab
- Bb Dorian #4Bb · C · Db · E · F · G · Ab
Understanding the Bb Half-diminished chord
Names and symbols
Bbm7b5 is the chord symbol for Bb Half-diminished; it is also written Bbø, Bbø7, Bb-7b5, Bbh7, Bbh.
The half-diminished seventh is written m7♭5 on charts and ø7 (or just ø) in jazz notation; both name the same four notes. It is not the diminished seventh, °7, whose seventh is a semitone lower.
Bb Half-diminished and A# Half-diminished are the same sound spelled two ways; both have a page here, and each links to the other. A# Half-diminished
How it is built
On Bb it is Bb · Db · Fb · Ab, stacking 1P · 3m · 5d · 7m. It is written m7♭5 or with the ø symbol, and both mean the same thing: a diminished triad softened by a minor rather than a diminished seventh.
How it is used
It is the ii of a minor ii–V–i, which makes it one of the most frequently played chords in jazz despite sounding exotic in isolation. It is also the chord built on the seventh degree of a major scale.
Unlike the fully diminished seventh it is not symmetrical, so it has a clear home and a clear direction: down a fifth, to the dominant.
Learn this properly
Chapter 10: Chords: Triads and SeventhsCommon questions
- What notes are in Bbm7b5?
- Bbm7b5 contains Bb · Db · Fb · Ab. Name any set of notes with the chord identifier.
- What is the difference between half-diminished and fully diminished?
- The seventh. Half-diminished uses a minor seventh; fully diminished lowers it again to a diminished seventh, which makes the chord symmetrical.
- Where is a half-diminished chord used?
- As the ii of a minor ii–V–i, and as the chord built on the seventh degree of a major scale.
- What notes are in the Bb Half-diminished chord?
- The Bb Half-diminished chord contains the notes Bb · Db · Fb · Ab: the root Bb with the intervals 1P, 3m, 5d, 7m stacked above it. Play them together for the chord or one after another for an arpeggio. The lowest note is normally Bb, but any chord tone can take the bass in an inversion.
- What intervals make up the Bb Half-diminished chord?
- Measured from Bb, the Bb Half-diminished chord stacks the intervals 1P, 3m, 5d, 7m. The quality of the third and of the seventh, if there is one, is what gives the chord its character; the rest of the notes colour it. Every interval in the formula links to its own page, with its sound.