7th Chords (The Complete Guide)

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 what chords should you learn next? Usually, the answer is 7th chords.

But, what are 7th chords?
7th chords are triads with an additional note added. The most common is the dominant 7th (aka major minor 7th) which is a major triad with an added minor 7th. Other types include 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.

This article serves as a general overview of 7th chords. If you are looking for information on a specific type of 7th chord, click one of the links below:

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.

For example, a dominant 7th chord consists of a blend of major and minor intervals along with a tritone (3 whole steps) between the 3rd and 7th. This creates dissonance and is responsible for the signature bluesy sound.

I’ve included audio samples below of the four most common 7th chords.

C7

Cmaj7

Cmin7

C7b5 (C half-diminished)

Cdim7

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. For a more details breakdown of each click on the links in the table.

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.

When to play 7th chords

Realistically, you can play them wherever you like, provided they sound good. But in most cases, as they tend to sound less stable, 7th chords introduce tension that 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 playing bring additional nuance to chord progressions compared to triads, allowing for greater expression when writing music.

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.