Diminished Seventh, Major Sixth, and Minor Sixth Chords
In this lesson, we’ll explore diminished seventh chords, major sixth chords, and minor sixth chords. Previously, you learned how to build and invert major, minor, and dominant seventh chords. Now, we’ll expand your toolkit with these three additional chord types.
Diminished Seventh Chords
A diminished seventh chord is built by stacking three minor thirds (root + minor third + diminished fifth + diminished seventh).
- Formula: Root → m3 → d5 → d7.
- Example in C:
Cdim7: C, Eb, Gb, A.
default:
Piano.Keyboard:
children: Cdim7
octaves: 1
Key Fact:
There are only three unique diminished seventh chords due to enharmonic equivalency:
- Cdim7 = Ebdim7 = Gbdim7 = Adim7
- C#dim7 = Edim7 = Gdim7 = Bbdim7
- Ddim7 = Fdim7 = Abdim7 = Bdim7
default:
Piano.Chart_cdim7:
children: Cdim7, Ebdim7, Gbdim7, Adim7
label: Cdim7 = Ebdim7 = Gbdim7 = Adim7
Piano.Chart_c#dim7:
children: C#dim7, Edim7, Gdim7, Bbdim7
label: C#dim7 = Edim7 = Gdim7 = Bbdim7
Piano.Chart_Ddim7:
children: Ddim7, Fdim7, Abdim7, Bdim7
label: Ddim7 = Fdim7 = Abdim7 = Bdim7
default:
Piano.Keyboard:
children: Cdim7
octaves: 1
Half-Diminished Seventh Chords (Min7♭5)
The vii° chord in a major scale is a half-diminished seventh chord (min7♭5), also written as ø.
- Formula: Root + m3 + d5 + m7.
- Example in B:
Bø7 (Bmin7♭5): B, D, F, A.
default:
Piano.Chart:
children: Bm7b5
start: B0
last: B1
Major Sixth Chords
A major sixth chord adds a major sixth interval to a major triad.
- Formula: Major Triad + Major 6th.
- Example in C:
C6: C, E, G, A.
default:
Piano.Keyboard:
children: C6
octavs: 1
Relationship to Minor Seventh Chords:
A major sixth chord is equivalent to a minor seventh chord rooted a minor third below.
- C6 = Amin7 (same notes: A, C, E, G).
default:
Piano.Keyboard:
children: C6
octavs: 1
default:
Piano.Chart:
children: C6, Am7
octavs: 1
label: C6 = Am7
Minor Sixth Chords
A minor sixth chord adds a major sixth interval to a minor triad.
- Formula: Minor Triad + Major 6th.
- Example in C:
Cm6: C, Eb, G, A.
default:
Piano.Keyboard:
children: Cm6
octavs: 1
Relationship to Half-Diminished Chords:
A minor sixth chord is equivalent to a half-diminished seventh chord rooted a minor third below.
- Cm6 = Aø7 (same notes: A, C, Eb, G).
default:
Piano.Keyboard:
children: Cm6
octavs: 1
default:
Piano.Chart:
children: Cm6, Am7b5
octavs: 1
label: Cm6 = Am7b5
Chord Equivalency Charts
Major 6th ↔ Minor 7th
| Major 6th Chord | Equivalent Minor 7th Chord |
|---|---|
| C6 | Amin7 |
| C#6 / Db6 | A#min7 / Bbmin7 |
| D6 | Bmin7 |
| D#6 / Eb6 | Cmin7 |
| E6 | C#min7 / Dbmin7 |
| F6 | Dmin7 |
| F#6 / Gb6 | D#min7 / Ebmin7 |
| G6 | Emin7 |
| G#6 / Ab6 | Fmin7 |
| A6 | F#min7 / Gbmin7 |
| A#6 / Bb6 | Gmin7 |
| B6 | G#min7 / Abmin7 |
Minor 6th ↔ Half-Diminished 7th
| Minor 6th Chord | Equivalent Half-Diminished 7th Chord |
|---|---|
| Cm6 | Aø7 (Amin7♭5) |
| C#m6 / Dbm6 | A#ø7 / Bbø7 |
| Dm6 | Bø7 |
| D#m6 / Ebm6 | Cø7 |
| Em6 | C#ø7 / Dbø7 |
| Fm6 | Dø7 |
| F#m6 / Gbm6 | D#ø7 / Ebø7 |
| Gm6 | Eø7 |
| G#m6 / Abm6 | Fø7 |
| Am6 | F#ø7 / Gbø7 |
| A#m6 / Bbm6 | Gø7 |
| Bm6 | G#ø7 / Abø7 |
Practical Applications
- Diminished Seventh Chords:
- Use as passing chords for chromatic movement (e.g., Cdim7 → Dm7).
- Major Sixth Chords:
- Add a jazzy, open sound to progressions (e.g., C6 → Fmaj7).
- Minor Sixth Chords:
- Substitute for half-diminished chords in minor key progressions (e.g., Cm6 → F7).
Example Progressions
- Diminished Passing Progression:
Cmaj7 → Cdim7 → Dm7 → G7 → Cmaj7. - Major Sixth Substitution:
Amin7 (C6) → Dm7 → G7 → Cmaj7. - Minor Sixth Resolution:
Cm6 → F7 → Bbmaj7.
