C#m7b5 — C# half-diminished seventh chord

A diminished triad with a minor seventh added. Three minor thirds separated by a major third.

1 = C#
b3 = E
b5 = G
b7 = B

Symbol: C#m7b5
Root: C#
Quality: Half-diminished seventh
Family: seventh
Notes: C# E G B
Degree formula: 1 b3 b5 b7
Semitones from the root: 0 3 6 10
Distinct pitch classes: 4
Interval structure: Stacked from the root: 3 semitones, 3 semitones, 4 semitones
Notation: Written m7b5 or with a slashed circle. The chord on the seventh degree of a major key, and the ii chord in a minor ii-V-i.
Key: C# · C# major / A# minor key signature

Formula

The chord tones in order from the root, with the interval each one forms above it.

Degree	Note	Semitones	Interval from the root
1	C#	0	Perfect unison
b3	E	3	Minor third
b5	G	6	Tritone
b7	B	10	Minor seventh

Degree

Note

Semitones

Interval from the root

Perfect unison

Minor third

Tritone

Minor seventh

Inversions

An inversion is the same set of notes with a different one in the bass. The last column gives the distance of each note above the bass note, in semitones.

Inversion	Bass note	Degree in the bass	Notes above the bass	Semitones above the bass
root position	C#	1	C# – E – G – B	0 3 6 10
first inversion	E	b3	E – G – B – C#	0 3 7 9
second inversion	G	b5	G – B – C# – E	0 4 6 9
third inversion	B	b7	B – C# – E – G	0 2 5 8

Inversion

Bass note

Degree in the bass

Notes above the bass

Semitones above the bass

root position

C# – E – G – B

0 3 6 10

first inversion

E – G – B – C#

0 3 7 9

second inversion

G – B – C# – E

0 4 6 9

third inversion

B – C# – E – G

0 2 5 8

Playable voicings

These shapes were found by searching the fretboard of a standard-tuned guitar (E A D G B E) rather than copied from a chord book. The search allows every string to sound or to be muted, rejects any shape with a muted string between two sounding strings, rejects any shape whose fretted notes span more than four frets (a five-fret window), requires every chord tone to be present, and then sorts what remains with root-position shapes first and the most compact, lowest shapes next. The shapes shown are the first six of that ordering; other orderings are possible at the same frets.

#	Shape (low string first)	Notes	Degrees	Bass	Span (frets)	Sounding strings
1	9-7-9-9-8-7 (6→1)	C# E B E G B	1 b3 b7 b3 b5 b7	C#	2	6
2	9-7-9-9-8-9 (6→1)	C# E B E G C#	1 b3 b7 b3 b5 1	C#	2	6
3	9-10-9-9-8-9 (6→1)	C# G B E G C#	1 b5 b7 b3 b5 1	C#	2	6
4	9-7-9-6-8-7 (6→1)	C# E B C# G B	1 b3 b7 1 b5 b7	C#	3	6
5	9-7-9-6-8-9 (6→1)	C# E B C# G C#	1 b3 b7 1 b5 1	C#	3	6
6	9-10-9-9-8-7 (6→1)	C# G B E G B	1 b5 b7 b3 b5 b7	C#	3	6

Shape numbers run from the lowest string to the highest, so the left-hand number is the sixth string (low E) in standard tuning. Multiple shapes are listed because a chord can be voiced several ways, and because a lower position is not always the better sounding one.

Related chords and scales

KeyEverything in C#scale, chords and neck map for this root
ScaleC# locrianthe scale this chord comes from
ChordC#dimthe triad underneath it
ChordF#m7the minor seventh a fifth below, from the same key

Everything in C# · All chords

KeyKey of C#C# D# E# F# G# A# B# · C# major / A# minor
ScaleC# locrian7 notes · 1 b2 b3 4 b5 b6 b7
ChordC#dim — Diminished1 b3 b5 · C# E G
ChordF#m7 — Minor seventh1 b3 5 b7 · F# A C# E
ChordC#dim7 — Diminished seventh1 b3 b5 bb7 · C# E G Bb
ChordC#7 — Dominant seventh1 3 5 b7 · C# E# G# B
ChordC#maj7 — Major seventh1 3 5 7 · C# E# G# B#
DegreesC# — degree mapC# major and natural minor · frets 0–22

Everything in this key: C# · Chords · Theory Atlas