7th Chords: Extending Triads
In the previous lesson, we learned how to build the four basic triads: major, minor, diminished and augmented.
We also looked at suspended three-note chord structures. These use a 2nd or 4th instead of a 3rd, so they are not triads.
In this lesson, we will add a 7th above the root to each type of three-note structure.
Starting three-note chord structure + type of 7th = 7th-chord formula
There are several kinds of 7th chord. The chord we create depends on two things:
- the three-note structure we begin with;
- the type of 7th we add.
A major 7th is written 7.
A minor 7th is written ♭7.
A fully diminished 7th chord uses a diminished 7th, written ♭♭7. We will meet that symbol in the diminished section.
Making 7th Chords from Major Triads
We begin with the major triad.
Its formula is:
1–3–5
Adding a 7th above the root of a major triad creates one of two common chords. The result depends on which 7th we add:
Major 7th Chord
If we add a major seventh (7) to a major triad, we get a major 7th chord:
1–3–5–7
Example in C:
This chord is most commonly written as:
CΔ7 is a common alternative symbol for the same chord.
Dominant 7th Chord
If we add a minor seventh (♭7) to the same major triad, we get a dominant 7th chord:
1–3–5–♭7
Example in C:
This chord is most commonly written as:
Making 7th Chords from Minor Triads
Next, we add a 7th to a minor triad.
The minor triad formula is:
1–♭3–5
When we add a seventh above the root, the quality of that seventh determines which type of chord we create.
Minor 7th Chord
If we add a minor seventh (♭7) to a minor triad, we get a minor 7th chord.
1–♭3–5–♭7
Example in C:
This chord is written as:
Minor-Major 7th Chord
If we add a major seventh (7) to the same minor triad, we get a minor-major 7th chord.
1–♭3–5–7
Example in C:
This chord is written as:
This less-common chord appears in jazz and film music, where the major 7th is retained above a minor triad.
Extending the Augmented Triad
An augmented triad has a raised 5th.
Its formula is:
1–3–♯5
Additional Seventh-Chord Type: Augmented-Major 7th Chord
If we add a major seventh (7) to an augmented triad, we get an augmented major 7th chord.
1–3–♯5–7
Example in C:
This chord is written as:
Augmented Dominant 7th Chord
If we raise the 5th of a dominant 7th chord, we get an augmented dominant chord.
1–3–♯5–♭7
Example in C:
This chord is written as:
C7♯5 is the clearer symbol because it identifies the dominant 7th structure and raised 5th; C+7 is an alternative symbol.
Diminished 7th Chords
A diminished triad contains a minor 3rd and a diminished 5th.
Formula:
1–♭3–♭5
Example in C:
C Diminished Triad (Cdim)
The two main diminished 7th chords add either a minor 7th (♭7) or a diminished 7th (♭♭7).
Half-Diminished 7th Chord
If we extend this chord by adding a ♭7 above the root, we get the half-diminished 7th chord.
1–♭3–♭5–♭7
Example in C:
This chord is commonly written as:
Fully Diminished 7th Chord
If we lower the seventh one more semitone, the interval becomes a diminished seventh, written ♭♭7.
1–♭3–♭5–♭♭7
Example in C:
This chord is called a fully diminished 7th chord, written:
B♭♭ sounds the same as A in equal temperament. It is written as a form of B because it functions as the 7th of the chord.
Additional Seventh-Chord Type: Diminished-Major 7th Chord
It is also technically possible to extend a diminished triad by adding a major seventh (7):
1–♭3–♭5–7
Example in C:
This chord is sometimes called a diminished-major 7th chord, written:
This diminished-major 7th chord is less common than the half-diminished and fully diminished forms.
Suspended Chords with a 7th
Suspended chords are three-note structures in which the 3rd is replaced by a major 2nd or perfect 4th. Because they contain no 3rd, sus2 and sus4 chords are neither major nor minor.
The two most common suspended structures are:
Example in C:
Suspended structures can also include a 7th, producing four-note formulas such as the examples below.
7sus4 Chord
Adding a minor 7th (♭7) to a sus4 structure creates a 7sus4 chord:
1–4–5–♭7
Example in C:
This chord is written as:
This is by far the most common suspended 7th chord and appears frequently in pop, rock, and gospel harmony.
7sus2 Chord
Adding a minor 7th (♭7) to a sus2 structure creates a 7sus2 chord:
1–2–5–♭7
Example in C:
Written as:
This chord is less common than the sus4 version but follows the same principle.
Additional Seventh-Chord Types: Major 7 Suspended Chords
In theory we could also add a major seventh (7) instead of a ♭7, producing chords such as:
Cmaj7sus4
1–4–5–7
Cmaj7sus2
1–2–5–7
Major 7 suspended chords are less common than dominant 7sus4 chords.
Suspended chords commonly create movement into a major or minor chord when the suspended note moves to the 3rd. Adding a ♭7 creates the particularly common dominant 7sus4 sound, but suspended structures are also widely used without a 7th.
Although the name comes from traditional suspension and resolution, modern music often uses sus chords as independent chord colours.
Seventh Chord Comparison
The table below summarises the most important seventh-chord types covered in this lesson.
| Chord type | Formula | Notes from C | Symbol |
|---|
| Major 7 | 1 – 3 – 5 – 7 | C – E – G – B | Cmaj7 / CΔ7 |
|---|
| Dominant 7 | 1 – 3 – 5 – ♭7 | C – E – G – B♭ | C7 |
|---|
| Minor 7 | 1 – ♭3 – 5 – ♭7 | C – E♭ – G – B♭ | Cm7 |
|---|
| Minor-major 7 | 1 – ♭3 – 5 – 7 | C – E♭ – G – B | Cm(maj7) |
|---|
| Half-diminished 7 | 1 – ♭3 – ♭5 – ♭7 | C – E♭ – G♭ – B♭ | Cø7 |
|---|
| Fully diminished 7 | 1 – ♭3 – ♭5 – ♭♭7 | C – E♭ – G♭ – B♭♭ | C°7 |
|---|
| Augmented-major 7 | 1 – 3 – ♯5 – 7 | C – E – G♯ – B | Cmaj7♯5 |
|---|
| Augmented dominant 7 | 1 – 3 – ♯5 – ♭7 | C – E – G♯ – B♭ | C7♯5 |
|---|
| Dominant 7sus4 | 1 – 4 – 5 – ♭7 | C – F – G – B♭ | C7sus4 |
|---|
| Dominant 7sus2 | 1 – 2 – 5 – ♭7 | C – D – G – B♭ | C7sus2 |
|---|
You do not need to memorise every chord type immediately. Begin with major 7, dominant 7, minor 7, half-diminished 7 and fully diminished 7.
Why Seventh Chords Matter
Adding a 7th expands a three-note chord structure and creates new chord types.
The result depends on both the starting structure and the type of 7th added.
Quick Test
Click each question to reveal the answer.
What is added to a three-note chord structure in this lesson?
A 7th above the root. The type of 7th helps determine the resulting chord.
What is the difference between a major 7th chord and a dominant 7th chord?
Both use a major triad. A major 7th chord adds a major 7th, while a dominant 7th chord adds a minor 7th.
What is the interval formula for a minor 7th chord?
1 – ♭3 – 5 – ♭7.
How does a half-diminished 7th chord differ from a fully diminished 7th chord?
Half-diminished uses a minor 7th (♭7); fully diminished uses a diminished 7th (♭♭7).
Why is the final note of C diminished 7 written as B♭♭ rather than A?
It functions as the seventh of a C chord, so it must use some form of the letter B. Writing A would describe a sixth.
What happens to the third in a suspended seventh chord?
It is replaced by either a major 2nd or a perfect 4th.
Explore these formulas as playable voicings in the Guitar Chord Finder, then see where seventh chords occur within a key in How to Harmonise the Major Scale.
