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C diminished major 7th chord on guitar (CdimMaj7)
Also called or written CdimMaj7, CdimM7, C°M7, C augmented minor seventh or C minor seventh sharp five
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.
How it is built
Formula 1, ♭3, ♭5, 7
- Root positionC–E♭–G♭–BCdimMaj7×-3-4-4-4-×
- First inversionE♭–G♭–B–CCdimMaj7/E♭×-6-×-5-7-7
- Second inversionG♭–B–C–E♭CdimMaj7/G♭2-2-1-×-1-2
- Third inversionB–C–E♭–G♭CdimMaj7/B×-×-9-8-7-8
How do you play a C diminished major 7th chord on guitar?
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.
Full note and interval 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 | — | — |
AdvancedThe four-fret span from the index on A3 to the pinky on B4 requires a wide stretch, and both E strings must stay silent.
8th fret
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.
Full note and interval 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
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.
Full note and interval 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
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.
Full note and interval 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
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.
Full note and interval 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 | — | — |
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.
Other C chords
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.