A#m7b5 A# half-diminished seventh chord
- Notes
- A# C# E G#
- Formula
- 1 b3 b5 b7
- Semitones
- 0 3 6 10 above the root
- Also written
- Bbm7b5 (Bb Db Fb Ab)
- Other symbols
- A#ø7, A#ø, A#m7(b5), A#min7b5
A# to C# is a minor third (3 semitones), C# to E is a minor third (3 semitones), E to G# is a major third (4 semitones). A diminished triad plus a minor seventh, G#, so A# to E is a tritone. It is also called half-diminished: the fully diminished A#dim7 has a diminished seventh (9 semitones) instead. With C# in the bass the same four keys read as C#m6.
A#m7b5 on the piano
Root position from A#4: A#4, C#5, E5, G#5. Middle C is C4.
A#m7b5 on the guitar
Standard tuning (E A D G B E). Strings run low E on the left to high e on the right, frets downwards; × is a muted string, ○ an open string, and each dot shows the note it sounds, with the root in blue-green. Every shape below has A# as its lowest note.
x 1 2 1 2 x (low E to high e)
Sounds A#2 E3 G#3 C#4
6 x 6 6 5 x (low E to high e)
Sounds A#2 G#3 C#4 E4
The E-shape and A-shape grips are movable: an E-shape chord's root is the note under your first finger on the low E string, an A-shape chord's root is the note on the A string. Slide the same grip up or down to play half-diminished seventh chords on other roots.
Inversions of A#m7b5
An inversion puts a note other than the root in the bass. The name is what semicord's chord finder calls those notes played bottom to top; a slash name like C/E means a C chord with E in the bass.
| Position | Notes, bass first | Named | Listen |
|---|---|---|---|
| Root position | A# C# E G# | A#m7b5 | |
| 1st inversion | C# E G# A# | C#m6 (also read as A#m7b5/C#) | |
| 2nd inversion | E G# A# C# | A#m7b5/E | |
| 3rd inversion | G# A# C# E | A#m7b5/G# |
Where A#m7b5 fits
A#m7b5 is viiø7 in B major, iiø7 in G# minor. As iiø7 it opens the minor ii–V–i: A#m7b5 → D#7 → G#m, the minor-key twin of the ii–V–I.