Tools / Chords / C diminished major 7th

C diminished major 7th chord on guitar (CdimMaj7)

Also written CdimMaj7, CdimM7 or C°M7

C diminished major 7th is built from C, E♭, G♭ and B. The 3rd fret shape stacks four close notes and mutes both E strings.

3rd fret×-3-4-4-4-×

Positions on the neck1 of 5

How it’s built

C1Root

E♭♭3Minor 3rd

G♭♭5Diminished 5th

B7Major 7th

Formula 1, ♭3, ♭5, 7

Positions on the neck1 of 5

Inversions

The same three notes, with a different one in the bass.

Root positionC–E♭–G♭–BCdimMaj7Bass C

First inversionE♭–G♭–B–CCdimMaj7/E♭Bass E♭

Second inversionG♭–B–C–E♭CdimMaj7/G♭Bass G♭

Third inversionB–C–E♭–G♭CdimMaj7/BBass B

Why it sounds like that

C diminished major 7th uses the formula 1, ♭3, ♭5, 7. The minor 3rd between C and E♭ darkens the chord, while the major 7th B adds a sharp leading tone. Compare it to C minor 7th flat 5th, which lowers the 7th to B♭.

What goes wrong with C diminished major 7th?

Letting the high e string ring open and clash with the chord.
Muting the G string with the ring finger while reaching for the B string.

When to use it

C diminished major 7th appears in C minor contexts as a passing chord, often resolving to C minor or C major 7th. The leading tone B pulls strongly to C, so use it before a C major cadence. It fits dark jazz and modern classical textures.

Changing to and from C diminished major 7th

Sliding the shape down one fret to the 2nd fret gives B diminished major 7th.

Which voicing to use

The 3rd fret shape is the default and keeps the bass on C. The 8th fret position moves the same voicing up an octave, while the 10th fret adds a higher register for melodic work.

How do you play a C diminished major 7th chord on guitar?

3rd fret

Intermediate● On the diagram

C diminished major 7th is played at the 3rd fret as × 3 4 4 4 ×: index finger on the A string at fret 3, middle finger on the D string at fret 4, ring finger on the G string at fret 4 and pinky finger on the B string at fret 4. The low E and high e strings stay muted.

Tip — The four-fret span from the index on A3 to the pinky on B4 requires a wide stretch, and both E strings must stay silent.

String-by-string breakdown

String	Fret	Finger	Note
6 (E)	muted	—	—
5 (A)	3	1	C (1)
4 (D)	4	2	G♭ (♭5)
3 (G)	4	3	B (7)
2 (B)	4	4	E♭ (♭3)
1 (e)	muted	—	—

8th fret

Intermediate

C diminished major 7th is played at the 8th fret as 8 9 9 8 × ×: index finger on the low E string at fret 8, ring finger on the A string at fret 9, pinky finger on the D string at fret 9 and middle finger on the G string at fret 8. The B and high e strings stay muted.

String-by-string breakdown

String	Fret	Finger	Note
6 (E)	8	1	C (1)
5 (A)	9	3	G♭ (♭5)
4 (D)	9	4	B (7)
3 (G)	8	2	E♭ (♭3)
2 (B)	muted	—	—
1 (e)	muted	—	—

10th fret

Intermediate

C diminished major 7th is played at the 10th fret as × × 10 11 12 11: index finger on the D string at fret 10, middle finger on the G string at fret 11, pinky finger on the B string at fret 12 and ring finger on the high e string at fret 11. The low E and A strings stay muted.

String-by-string breakdown

String	Fret	Finger	Note
6 (E)	muted	—	—
5 (A)	muted	—	—
4 (D)	10	1	C (1)
3 (G)	11	2	G♭ (♭5)
2 (B)	12	4	B (7)
1 (e)	11	3	E♭ (♭3)

CdimM7/E♭ inversion · fret 5

Intermediate

C diminished major 7th is played at the 5th fret as × 6 × 5 7 7: middle finger on the A string at fret 6, index finger on the G string at fret 5, ring finger on the B string at fret 7 and pinky finger on the high e string at fret 7. The low E and D strings stay muted.

String-by-string breakdown

String	Fret	Finger	Note
6 (E)	muted	—	—
5 (A)	6	2	E♭ (♭3)
4 (D)	muted	—	—
3 (G)	5	1	C (1)
2 (B)	7	3	G♭ (♭5)
1 (e)	7	4	B (7)

CdimM7/E♭ inversion · fret 10

Intermediate

C diminished major 7th is played at the 10th fret as 11 × 10 11 12 ×: middle finger on the low E string at fret 11, index finger on the D string at fret 10, ring finger on the G string at fret 11 and pinky finger on the B string at fret 12. The A and high e strings stay muted.

String-by-string breakdown

String	Fret	Finger	Note
6 (E)	11	2	E♭ (♭3)
5 (A)	muted	—	—
4 (D)	10	1	C (1)
3 (G)	11	3	G♭ (♭5)
2 (B)	12	4	B (7)
1 (e)	muted	—	—

Common questions

How is C diminished major 7th written?

C diminished major 7th is written C°M7 or CdimM7.

What is the difference between C diminished major 7th and C minor 7th flat 5th?

C diminished major 7th has a major 7th, B. C minor 7th flat 5th lowers that note to B♭, giving a dominant-quality chord.

Why does C diminished major 7th sound so unstable?

The diminished 5th between C and G♭ creates a tritone, and the major 7th B sits a semitone below the octave. Both intervals demand resolution.

String

Fret

Finger

Note

6 (E)

muted

—

5 (A)

C (1)

4 (D)

G♭ (♭5)

3 (G)

B (7)

2 (B)

E♭ (♭3)

1 (e)

muted

—

String

Fret

Finger

Note

6 (E)

C (1)

5 (A)

G♭ (♭5)

4 (D)

B (7)

3 (G)

E♭ (♭3)

2 (B)

muted

—

1 (e)

muted

—

String

Fret

Finger

Note

6 (E)

muted

—

5 (A)

muted

—

4 (D)

C (1)

3 (G)

G♭ (♭5)

2 (B)

B (7)

1 (e)

E♭ (♭3)

String

Fret

Finger

Note

6 (E)

muted

—

5 (A)

E♭ (♭3)

4 (D)

muted

—

3 (G)

C (1)

2 (B)

G♭ (♭5)

1 (e)

B (7)

String

Fret

Finger

Note

6 (E)

E♭ (♭3)

5 (A)

muted

—

4 (D)

C (1)

3 (G)

G♭ (♭5)

2 (B)

B (7)

1 (e)

muted

—