Tag: dominant 7th chord

This post is the last of a 2-part series of free basic music theory lessons on my blog, musictheoryde-mystified.com. You can see the complete list here. Please feel welcome to make a comment or ask a question.

Major and minor triads form the basis of many other chords. Of these, by far the most well-known is the dominant 7th chord.

What’s a Dominant 7th Chord?

A dominant 7th is a major chord with an added minor 7th. It is so named because it is most popularly used as the chord on the dominant of the home key.

In C major, the chord on the dominant is G: G B D. Add a minor 7th, F, and we get G B D F.

It sounds a bit less solid than a plain major chord. Have a listen…

Triad

A triad is a chord whose content is made up of intervals of a 3rd (it doesn’t mean the chord has 3 notes). The extra note follows this pattern so a dominant 7th chord is a triad.

Although it has a 7th, we can still include the octave. Like any chord, the notes can be played in any pitch order and any of the notes can be doubled at other octaves. In the above example the notes were spread over 2 octaves for clarity.

7th Chords

Dominant 7th chords are often just called 7th chords or 7 chords. This can be confusing because there are also other types of 7th chords. However, broadly speaking, dominant 7ths are the most common. Unless specifically stated otherwise, it’s quite likely that a 7th chord would be a dominant 7th.

Chord Symbol

The main part of the chord is a major triad, indicated by the name of the root note. The minor 7th is written as a suffix after the chord name, the number 7.

Tritone

The dominant 7th chord contains a diminished 5th, an interval of 6 semitones, between the 3rd and 7th notes.

A 6-semitone interval is commonly called a tritone. A tritone is a dissonant interval. When you hear two notes 6 semitones apart, neither note supports the other. 

Adding this effect to a major chord makes the chord less stable. Since the 3rd is embedded in the major chord, it’s the 7th that feels unstable. When we hear it, we want it to move.

Usage 

A dominant 7th chord is most commonly used as a way to arrive in the home key at the conclusion of a phrase; V7 – I, or V7 – i if the piece is in a minor key.

There’s nothing wrong with using a plain major chord on the dominant but the instability of the 7th helps the chord to “tip over” on to the tonic, giving a satisfying sense of arrival at home.

Here the F in the G7 chord happily drops to E, which belongs to the tonic chord, C.

Tension and Resolution

In the above example, without the 7th, the chord change is a bit static; both chords feel quite stable. 

By adding the minor 7th, F, the tritone between the 3rd and 7th adds tension to the dominant chord. The listener is left with a sense of wanting to leave the unstable dominant and arrive solidly at home.

This arrival is called resolution. Tension and resolution is the main driving force in Western music. Dominant 7th chords are used in this way in many genres, old and new.

The dominant 7th can similarly be used on the tonic as a “pretend dominant” to lead away from a no-longer stable home to the subdominant, I – I7 – IV, and onwards…

You could say, if you want a chord to move along, make it a dominant 7th.

The Dominant 7th And The Chords Of The Major Scale

Remember the chords of the major scale from B20. The 6 Most Useful Chords In Any Major Key? That funny chord on the leading note turns out to be the top three notes of the dominant 7th chord. It’s a dominant 7th without the root note!

Aside: As a chord in its own right it’s known as a diminished triad. It’s a minor chord with a flattened 5th… but that’s a subject for my upcoming intermediate theory short course…

Other Uses

The dominant 7th chord can be used as a chord in its own right, purely for its character. In blues, for example, it’s quite common to play all the chords as dominant 7ths.

if you play a chord instrument, try replacing the major chords in any simple piece with dominant 7ths; it lends a bluesy quality to almost anything.

Dominant 7th In Minor Keys

The harmonic minor allows the dominant chord to be a major chord in a minor key, so the majority of pieces in minor keys also have a dominant 7th chord.

In the harmonic minor, the dominant 7th chord is the same as in the major key of that root note. For example, the dominant 7th of both C major and C minor is G7; the dominant 7th of both F major and F minor is C7.

How To Find The Notes of a Dominant 7th Chord

A dominant 7th chord is a major chord with an added minor 7th. It is made up of the 1st, Major 3rd, perfect 5th and minor 7th of the key it represents.

First, work out the notes of the major chord as described in B14. Chords 1: Major/Minor Triads And Modal Chords. 

Here are two ways to find the minor 7th:

Method 1

The 7th note is a minor 3rd above the 5th note of the chord. You can find it by counting 2 letters up from the 5th. 

If the chord is on the dominant of the overall key, the 7th is a scale note, so you won’t need to count semitones. Otherwise, make sure it’s 3 semitones above the 5th.

Method 2

The 7th note is also a major 2nd below the octave. It’s the letter below the octave.

Again, if the chord is on the dominant of the overall key, the 7th is a scale note. You have the answer. Otherwise, make sure it’s 2 semitones below the octave.

Try These…

1

As text, list the content (the different notes) of the following dominant 7th chords:

1. D7
2. A7
3. Bb7
4. Eb7
5. E7

2

Name the dominant 7th chord in the following keys:

1. D major
2. D minor
3. A minor
4. Bb major
5. C minor

Answers at the end of this post.

Inversions

A dominant 7th chord has 4 different notes, so there are 4 possible inversions: root position plus 1st, 2nd and 3rd inversion. The chord is in 3rd inversion when the 7th is the lowest note.

Having the 7th in the bass lends even more weight to the instability of the chord. It’s often used in the bass as part of a “bass run”, to help a chord move on to the next chord.

The dominant 7th is just one common example of the many different chords which are based on major or minor triads.

Congratulations!

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Answers to Try These…

1

1. D7 = D F# A C
2. A7 = A C# E G
3. Bb7 = Bb D F Ab
4. Eb7 = Eb G Bb Db
5. E7 = E G# B D

2

1. The dominant 7th chord of D major = A7
2. The dominant 7th chord of D minor = A7
3. The dominant 7th chord of A minor = E7
4. The dominant 7th chord of Bb major = F7
5. The dominant 7th chord of C minor = G7