What are 7th Chords?

When learning guitar, the first chords you are likely to encounter are major and minor triads (3 note chords). But once you have a decent grasp of these introductory chords (yes, even F major) what chords should you learn next? Usually, the answer is 7th chords.

7th chords are triads with an additional 7th interval added, making it a 4 note chord (Tetrad). The most common on guitar is the dominant 7th (aka major minor 7th) a major triad with an added minor 7th interval (10 semitones from the root), along with the major 7th, minor 7th, minor 7 flat 5, and diminished 7th.

In the following article, we’re going to take a closer look at 7th chords and the theory behind how they are constructed. We’ll also learn some useful (and moveable) shapes used to play them, and learn how to incorporate them into a chord progression.

How 7th Chords Are Written

One confusing aspect of 7th chords is how they are written. While note letter names without a suffix are regarded as Major, unless otherwise indicated, the opposite is true for the 7th interval.

For example, an Amaj7 chord should be read as an A + major 7 interval, not an A major chord with a 7th. The ‘A’ doesn’t require ‘maj’ to be written, it is implied as it is not indicated as minor (min), augmented (aug), or diminished (dim).

On the other hand, if there is no prefix in front of the 7 as is the case most of the time with a dominant 7th, usually written as C7 you can assume the 7th is a minor 7th interval (spanning 10 semitones from the root).

So, in the case of C7, we know the C is major with a minor 7th interval added, making C7 a dominant 7th aka a major-minor 7th.

Another example of this is the minor 7th, usually written Cmin7. In this case, the chord is a C minor triad with a minor 7 interval. If minor was not written it would be implied that the note letter name is major, and as we now know the 7 is considered minor unless indicated otherwise.

So, keep in mind if you see major written after the note letter this will always refer to the 7th interval. If you see minor, diminished, or augmented it will apply to the note letter name.

What do 7th chords sound like?

As a general rule 7th chords are more dissonant than triads.

While triads sound consonant (in agreement harmonically) the additional pitch added to form a 7th, makes the chord richer harmonically but also less in harmonic agreement.

C7

The blend of major and minor, and the tritone (3 whole steps) between the 3rd and 7th creates dissonance and is responsible for the signature bluesy sound.

Cmaj7

Major 7th chords sound very open, and jazzy.

Cmin7

Minor 7th chords sound similar to major 7 chords but as you might expect from a minor chord sound more melancholy.

C7b5 (C half-diminished)

Half-diminished 7th chords are tense and unstable. They are often used as passing chords before the V chord (aka they are often used as the predominant chord) in a chord progression.

Cdim7

The diminished 7th sound is even tenser and as a result, they are often used as the dominant chord before resolving to the tonic chord.

How are 7th Chords Built

7th chords are built on top of triads (i.e. major or minor triads) with an added 7th interval.

I’ve included the chord name, symbol, and scale degree formulas for each below.

ChordChord SymbolScale Degree Formula
Dominant 7th
(Major/minor 7th)
7, dom71, 3, 5, b7
Major 7thmaj7, M71, 3, 5, 7
Minor 7thM7, min7, -71, b3, 5, b7
Half Diminished 7th
(minor 7 flat 5)
ø71, b3, b5, b7
Diminished 7th
dim7, o71, b3, b5, bb7

Another way to build them is by stacking thirds, meaning we skip every second note letter name, the same way we build triads.

For example, CMaj7 consists of a C, (skip the D), E, (skip the F), G, (skip the A), and B.

C major 7 stacked thirds

This gives us the intervals of a major third between the C and E and a minor third between the E and G, just as we would find in a major triad. The interval between the 3rd (G) and 4th (B) notes is also a third, in this case, a major third.

Why thirds?
Thirds are consonant intervals, meaning they are pleasing to the ear. It’s generally accepted that the most consonant intervals are octaves, perfect fifths, perfect fourths, and thirds (both major and minor), and of course, unison as this refers to the same note. Another reason thirds are used often in chord construction is how the notes are distributed within their accompanying scale. If you consider a typical heptatonic (7 note) scale such as the major scale, thirds sound pleasing to our ears as there is an equal distribution of the notes within a given scale that the chord is derived from.

Dominant 7th chords

What are Dominant Chords?
Dominant chords are major triads with a minor 7th added, hence why they are also called major-minor chords. Dominant may also refer to the function of the chord within the chord scale e.g. the dominant chord, the V chord, is built on the 5th scale degree of a given key.

For example, in the key of A major E is the dominant chord, which can be substituted with an E7 chord as dominant chords can be used as the V chord in major keys (often written as V7) and the VII chord in minor keys. Their function, usually, is to direct the music back to the tonic.

If you would like to read more about dominant 7th chords, including chord charts, and more information on how they are constructed click here.

Major 7th Chords

Usually written as CM7 or Cmaj7

Major 7th chords are simply major triads with a major 7th interval (from the root) added.

You can all about major 7th chords, including how they are constructed here.

Minor 7th Chords

Usually written as Cmin7 or Cm7

If you know your triads, you have probably already worked out the difference between the major and minor 7th is the minor third and minor 7th intervals.

You can read all about minor 7th chords, including more information on how they are constructed here.


Half Diminished 7th (aka Minor 7 flat 5)

Half diminished 7th chords are also commonly referred to as minor 7 flat 5 chords. Taking this naming convention we can easily work out a half-diminished 7th is simply a minor 7th with a flattened 5th, making it diminished.

You can read more about half-diminished 7th chords, including more information on how they are constructed here.


Diminished 7th

The only difference between a half-diminished and diminished 7th chord is the minor 7th interval becomes a diminished 7th interval (°7) which is 9 semitones above the root, a minor 7th is 10 semitones.

Diminished 7th Chord Intervals

This means the chord is comprised of three stacked minor 3rds.

Our scale degree formula, in this case, is 1, ♭3, ♭5, ♭7

12♭34♭567
CDEFGAA

To form a Cdim7 chord we’re only moving the 7th note of the scale down a semitone if compared to the C half-diminished chord we formed above.

If starting from A major, however, we can slide up two frets (a whole step) on the 4th string to G♭ and fret the 2nd fret of the 3rd string to include the A. We can then move from the 1st fret on the 2nd string to include E♭. Lastly, as it can feel easier to play this chord shape when barring the 1,2, and 3 strings, we can include an additional G♭ on the 1st string.

C Major and Cdim7 Chord Charts

When to play 7th chords

Now that we know some useful moveable shapes, where do we play 7th chords?

Realistically, we can play them wherever we like, provided they sound good. But in most cases, as they tend to sound less stable, they introduce tension which demands resolution.

The information below makes a good starting point.

Dominant 7th chord function

Dominant 7ths are the most common 7th chords and are almost always played as the V chord, the dominant chord in major keys, and the VII chord in minor keys.

As the dominant 7th isn’t fully compliant with major keys, due to the minor 7th interval, it sounds unstable and feels as though it wants to resolve to the tonic chord.

Major 7th chord function

Major 7th chords can be played in place of major chords, meaning we can play them as I and IV chords in major keys and III and VI chords in minor keys. Major 7 chords sound jazzy and open.

Minor 7th chord function

Minor 7th chords can replace minor chords. This allows us to play minor 7th’s as the ii, iii, and vi chords in major keys and the i, iv, and v chords in minor keys. They sound similar to major 7th chords in many ways but as you would expect from a minor chord, sound more melancholy.

Half diminished 7th chord function

Half-diminished 7th chords are dissonant, and unusual on their own but add tension that is then released when moving to another chord.

Diminished 7th chords function

Diminished 7th chords are also commonly used as passing chords, resolving to major or minor chords a half step higher in pitch.

Summary

7th chords are the ideal place to begin building upon your existing chord theory and when incorporated into your own playing bring additional nuance to chord progressions compared to triads, allowing for greater expression when writing music. I hope the information above serves as a useful introduction to 7th chords in all their glory.

Marty

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My name’s Marty. I’ve been into guitars, songwriting, and home recording for over 30 years. Theacousticguitarist.com is my blog where I write about everything I have learned along the way.