A#dim7 A# diminished seventh chord
- Notes
- A# C# E G
- Formula
- 1 b3 b5 bb7
- Semitones
- 0 3 6 9 above the root
- Also written
- Bbdim7 (Bb Db Fb Abb)
- Other symbols
- A#°7, A#o7
A# to C# is a minor third (3 semitones), C# to E is a minor third (3 semitones), E to G is a minor third (3 semitones). Four notes each a minor third (3 semitones) apart, so the chord splits the octave into four equal parts and there are only three different diminished seventh chords. Every inversion is another diminished seventh named after its bass note: C#dim7, Edim7, Gdim7. The seventh is spelled G, a diminished seventh above A#: one letter name above the major sixth F## that sounds the same.
A#dim7 on the piano
Root position from A#4: A#4, C#5, E5, G5. Middle C is C4.
A#dim7 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 0 2 x (low E to high e)
Sounds A#2 E3 G3 C#4
6 x 5 6 5 x (low E to high e)
Sounds A#2 G3 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 diminished seventh chords on other roots.
Inversions of A#dim7
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#dim7 | |
| 1st inversion | C# E G A# | C#dim7 (also read as A#dim7/C#) | |
| 2nd inversion | E G A# C# | Edim7 (also read as A#dim7/E) | |
| 3rd inversion | G A# C# E | Gdim7 (also read as A#dim7/G) |
Where A#dim7 fits
A#dim7 is vii°7 in B minor. Its four notes are evenly spaced, so the same keys are a diminished seventh on each of them, and the chord can lead a half step up from any of its notes: to a chord on B, D, F or Ab. That is why it is the classic passing and pivot chord.