C#m7b5 C# half-diminished seventh chord
- Notes
- C# E G B
- Formula
- 1 b3 b5 b7
- Semitones
- 0 3 6 10 above the root
- Also written
- Dbm7b5 (Db Fb Abb Cb)
- Other symbols
- C#ø7, C#ø, C#m7(b5), C#min7b5
C# to E is a minor third (3 semitones), E to G is a minor third (3 semitones), G to B is a major third (4 semitones). A diminished triad plus a minor seventh, B, so C# to G is a tritone. It is also called half-diminished: the fully diminished C#dim7 has a diminished seventh (9 semitones) instead. With E in the bass the same four keys read as Em6.
C#m7b5 on the piano
Root position from C#4: C#4, E4, G4, B4. Middle C is C4.
C#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 C# as its lowest note.
x 4 5 4 5 x (low E to high e)
Sounds C#3 G3 B3 E4
9 x 9 9 8 x (low E to high e)
Sounds C#3 B3 E4 G4
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 C#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 | C# E G B | C#m7b5 | |
| 1st inversion | E G B C# | Em6 (also read as C#m7b5/E) | |
| 2nd inversion | G B C# E | C#m7b5/G | |
| 3rd inversion | B C# E G | C#m7b5/B |
Where C#m7b5 fits
C#m7b5 is viiø7 in D major, iiø7 in B minor. As iiø7 it opens the minor ii–V–i: C#m7b5 → F#7 → Bm, the minor-key twin of the ii–V–I.