Chords
A# Half-diminished
A# · C# · E · G#
The half-diminished seventh — a diminished triad with a minor seventh. The ii of a minor key.
Also written A#ø · A#ø7 · A#-7b5 · A#h7 · A#h
A# Half-diminished
A# · C# · E · G#
Voicings on the piano
| Voicing | Notes | Play it on your instrument |
|---|---|---|
| Closed, root position | A#3 · C#4 · E4 · G#4 | |
| Open (drop 2) | E3 · A#3 · C#4 · G#4 | |
| Shell | A#3 · C#4 · G#4 | |
| Rootless | C#4 · E4 · G#4 · A#4 |
Tap a key or a fret to hear it.
Anatomy
A# Half-diminished (A#m7b5) contains the notes A# · C# · E · G#, each with a role measured as an interval from the root.
Read on: how triads are built · seventh chords
Inversions
An inversion of A# Half-diminished puts a chord tone other than A# in the bass; the name after the slash is that bass note.
Where it lives
The keys and the scales A# Half-diminished belongs to.
In which keys
A# Half-diminished is diatonic to 3 keys; the numeral is its degree and the label its harmonic function.
Scales that contain it
A# Half-diminished fits inside these scales, each built on A#.
- A# Minor BluesA# · C# · D# · E · E# · G#
- A# LocrianA# · B · C# · D# · E · F# · G#
- A# Locrian PentatonicA# · C# · D# · E · G#
- A# Super Locrian PentatonicA# · C# · D · E · G#
- A# Locrian #2A# · B# · C# · D# · E · F# · G#
- A# Bebop LocrianA# · B · C# · D# · E · E# · F# · G#
Understanding the A# Half-diminished chord
Names and symbols
A#m7b5 is the chord symbol for A# Half-diminished; it is also written A#ø, A#ø7, A#-7b5, A#h7, A#h.
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.
A# Half-diminished and Bb Half-diminished are the same sound spelled two ways; both have a page here, and each links to the other. Bb Half-diminished
How it is built
On A# it is A# · C# · E · G#, 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 A#m7b5?
- A#m7b5 contains A# · C# · E · G#. 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 A# Half-diminished chord?
- The A# Half-diminished chord contains the notes A# · C# · E · G#: the root A# 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 A#, but any chord tone can take the bass in an inversion.
- What intervals make up the A# Half-diminished chord?
- Measured from A#, the A# 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.