Chord theory 2 - Seventh chords

This is the second of four pages about chords. Each page dives into the details about one particular kind of chord:

1. triads
2. seventh chords
3. added note chords
4. extended chords

Before getting into more chords, we're going to introduce some more ideas, which will make it much easier to discuss chords.

What is a scale?

If we play the white notes on a piano, starting at C, then this is the scale of C major.

• C, D, E, F, G, A, B, C

You may also know this scale using the notes:

• do, re, mi, fa, so, la, ti, do

for example from the famous song Do-Re-Mi in the film The sound of music.

By the way, we usually use the letters C, D, E etc. in English, but this is not universal. In many other languages, a scale similar to do-re-mi is used. For example, in Italian, the scale is:

• do, re, mi, fa, sol, la, si, do

We have already discussed the idea of a root note in a chord. In a similar way, there is a note at the base of a scale, which is called the tonic.

Now let's imagine, we start at the note G, and build the same major scale. In this case we need the notes:

• G, A, B, C, D, E, F♯, G

Let's compare the C major scale with the G major scale on the piano keyboard.

Instead of using all the white notes, we have shifted the note F up one semitone to the note F♯. We have to do this to keep the same separation between the notes.

In the C major scale, the notes are separated by a fixed number of semitones:

In the G major scale, we have to keep same separation between the notes, which is why we move the F up one semitone to F♯.

Note:
So far we have only talked about major scales. There are also three different kinds of minor scale, but I'm not going to discuss them in these pages about chords.

What is a key?

If a piece of music mainly uses the notes in a particular scale, for example the C major scale, we say that the music is in the key of C.

The note at the base of a scale is called the tonic. We use the same name in a key, so the tonic in key of C it the note C.

The tonic plays an important role, because it feels like a home note. A lot of pieces of music end on the tonic and end using chord based on the tonic. This gives them a feeling of going home.

Note:
Keys have a special importance in musical notation, where they are indicated using a so called key signature.

Scale degrees

We can talk about the notes in the C major scale (C,D,E,F,G,A,B,C) or in the G major scale (G,A,B,C,D,E,F♯,G), but it useful to talk about the notes without using a specific scale.

The position of a note in a scale is called the scale degree, but we can also just call it the position, or the note position.

There are different ways to talk about them:

• using names, like the tonic or the dominant
• using position, like the third or the fifth
• using roman numeral notation

We'll discuss roman numeral notation in the next section. First let's look at the names and the scale degree numbers.

The subtonic doesn't quite fit into the scheme, but I have added it for completeness.

Some of the names come in pairs

• dominant and subdominant
  (one 5th above the tonic or below the octave)
• mediant and submediant
  (one 3rd above the tonic or below the octave)
• supertonic and subtonic
  (two semitones above the tonic or below the octave)

These names come from musical theory, and sound a bit fancy. I will use the term tonic, but otherwise just use the position.

Note: The scale degree is a lot like the chord factor. Technically:

• the scale degree describes the position of a note in a scale
• the chord factor describes the position of a note in a chord

Roman numeral notation

Firstly, if you don't know what Roman Numerals are, then you can read about them on wikipedia. It's how the Romans wrote numbers.

Roman numeral notation is just a notation. Nobody uses it in speech.

Here is a quick overview of the roman numerals used.

We aren't going to use roman numeral notation much, but it is useful for desribing some chord sequences.

Chord symbols

Chord symbols are a very important way of writing down music. For many guitar and piano players, they are more important than notes written in formal music notation.

You can find chord symbols:

• often written above musical notation
• on internet sites with song lyrics and chords (but no musical notation)
• on jazz lead sheets, which have musical notation of a melody, with chord symbols for the harmonies

In the simplest form, a chord symbol is a single letter, for example C indicates a C major triad.

The letter may be accompanied by a sharp (♯) or flat symbol (♭), so for example E♭ indicates an E♭ major triad.

So far we have only discussed the four triads, so let's look at the chord symbols for those chords:

In jazz lead sheets, it is very common for a minor chord to be indicated with a hyphen (C-). A minor chord may also be indicated with a lower case letter, but that is not so common.

From now on, we will show the chord symbol when we introduce new chords.

You can also use roman numeral notation in chord symbols. For example V would mean a major triad, built on the fifth note of a scale. Using romam nueral notation, minor chords are always indicated using lower case. For example ii would indicate a minor triad on the second note of a scale.

Movable guitar chords

From now on, when we discuss chords, we're going to look at each chord on the piano keyboard, usually with the root C. You can translate the chord to a different root, by moving all the notes up or down, so that the intervals between the notes do not change.

We're not going to get into the details of how you might play different voicings, a how you might split the notes up between the left and the right hand.

For the guitar, we are going to take a different approach and look specifically at movable chords. Movable chords are chords which do not contain any open strings.

Because there are no open strings, you can move the chord up and down the fretboard to play it with different root notes, so long as you keep the same chord shape.

Here are some examples of a movable 7 chord, with the root on string 4.

We are going to look at versions of the chord:

• with the root on string 6 (the E-string)
• with the root on string 5 (the A-string)
• with the root on string 4 (the D-string)

In each case we will look at:

• a conceptual shape, with the notes in ascending order
• a playable shape, where the root is lowest note, but the other notes may be rearranged

In the examples, we will place the root on fret 7, so that we have enough space to its left.
The means that the root notes will be:

• B on string 6
• E on string 5
• A on string 4

All in all, this means that we will be taking more space with guitar chords than with piano chords.

Seventh Chords

So far, we have discussed a lot of basic ideas about chords, and learned how to build triads.

Now we are going to contiune our exploration of chords by looking at seventh chords.

How to build seventh chords

When we looked at triads, we used the technique of stacking thirds. We are going to extend this idea to build chords with 4 notes.

The idea is:

• we start with the root note,
• we add a third to get the second note in the chord
• we add another third to get the third note in the chord
• we add another third to get the fourth note in the chord

In each case, the third may be a minor third (3 semitones) or a major third (4 semitones).

The chord factors in a seventh cord are always 1, 3, 5 and 7.

This gives us a total of 8 combinations:

Note: The symbol may be written as a superscript, for example C⁷ rather than C7. This is usually not important.

Let's take a look at this chords and let's start with the ones which we can play by using only the white notes on a piano.

Dominant seventh chord

The fifth note in the scale is known as the dominant. In the C major scale (the white notes on a piano), the dominant is G.

This is the only note on which we can build a dominant seventh chord using only the white notes.

The dominant 7th is what we think of as a "normal" 7th chord. If you at the fingering for a 7th chord on a guitar, it is invariably a dominant 7th chord.

Movable guitar chords

As described above, we are going to look at the shape of movable guitar chords with the root on the strings 6, 5 and 4, and consider:

• a conceptual shape, with the notes in ascending order
• a playable shape, where the root is lowest note, but the other notes may be rearranged

V7-I sequence

The dominant seventh chord is very often used in a sequence of:

• the dominant seventh on the fifth note
• the major triad on the tonic

Using roman numeral notation, we can describe that sequence as V7-I.

In the key of C, that means going from G dominant seventh to a C major triad.

Let's look at an example in the key of C on the piano, and on the guitar.

If we leave out the 5th note in the G7 chord, we can see how the notes move from one chord to the next. The 5th note is usually the least important note.

The idea is, that the note B wants to move up to the note C and the note F wants to move down to the note E. We somehow expect the G7 chord to be followed by the C chord.

Musicians sometimes say that the G7 chord is resolved to the C chord, because the sense of expectation has been fulfilled.

Because this sequence ends on the tonic, a lot music ends with ths sequence.

Note: The expectation that the dominant seventh chord will be followed by the tonic might be due to some intrisic qualities of the chords, or it might just be a convention that we have learned by hearing western music. You can make up your own mind about that.

Using open guitar chords, the sequence G7-C is

The dominant seventh chord is the most common seventh chord in all western music.

Major seventh chord

You can build a major seventh chord using the white notes on a piano, starting on C or F.

The major seventh chord is widely used, in particular in jazz. Unlike the dominant seventh chord, it does not have the feeling of pulling towards the tonic.

Movable guitar chords

Once again, we are going to look at the shape of movable guitar chords with the root on the strings 6, 5 and 4, and consider:

• a conceptual shape, with the notes in ascending order
• a playable shape, where the root is lowest note, but the other notes may be rearranged

Minor seventh chord

You can build a minor seventh chord using the white notes on a piano, starting on D, E or A.

The minor seventh chord is also very widely used.

Movable guitar chords

As before, we are going to look at the shape of movable guitar chords with the root on the strings 6, 5 and 4.

ii7-V7-I sequence

We already discussed the chord sequence V7-I. Now is a good time to describe another very common sequence, which is ii7-V7-I.

This is a sequence of:

• a minor seventh chord on the second in the scale (supertonic) (ii7)
• a dominant seventh chord on the fifth not in the scale (dominant) (V7)
• a major triad on the tonic (I)

Note: The chord symbol ii7 uses lower case roman numeral notation to indicate a minor chord.

This very common sequence is typically called ii-V-I, without explicitly specifying the 7, or simply as 2-5-1.

Let's look at an example in the key of C, first on the piano and then on the guitar.

This example uses an inversion of the G7, so that is stays in the same position on the keyboard and uses some of the same notes.

Here is a version of the ii7-V7-I sequence using movable guitar chords.

Half diminished seventh chord

This chord is also called the minor 7th flat 5. This name is commonly used by guitar players.

You can build a half diminished seventh chord using the white notes on a piano, starting on B. The half dimiinished seventh chord is obviously named with reference to the diminished seventh chord.

Movable guitar chords

Here are the shapes of the minor 7th flat 5 chord as movable guitar chords with the root on the strings 6, 5 and 4.

Diminished seventh chord

All of the seventh chords discussed so far, can be built using only the white notes on a piano. That is not true of the diminished seventh chord.

The diminished seventh chord has some very interesting properties.

• All of the notes are are separated by a minor third, or by 3 semitones.
• The first octave of the root is 12 semitones above the root.
  That means that the separation between the fourth note in the chord, and the first octave is also three notes.
• All of the separations are 3 semitones!

Let's take a look at the C diminished seventh (C^o7) chord and see what happens when we make inversions of the chord.

Here's the thing:

• The first inversion of the C diminished 7th chord
  is identical to an E♭ diminished 7th chord
• The second inversion of the C diminished 7th chord
  is identical to an G♭ diminished 7th chord
• The third inversion of the C diminished 7th chord
  is identical to an A diminished 7th chord
• The fourth inversion of the C diminished 7th chord
  is a C diminished 7th chord

So when you play a C diminished 7th chord, there are 4 different ways to hear it.

In fact, there are only three different diminished 7th chords, and each one can be interpreted in 4 different ways.

This gives diminished seventh chords a strange disorientating quality, where you don't quite know where you are. You might find that they have a spooky quality, or that they create a feeling of suspense.

In a chord sequence, diminished seventh chords can be used to bridge between other chords, by going via a sort of no man's land.

Movable guitar chords

Here are the shapes of the diminished 7th chord as movable guitar chords with the root on the strings 6, 5 and 4.

Minor major seventh

A minor major seventh chord is a combination of a minor triad, and a major seventh.

This is what a C minor major seventh chord looks like on the piano keyboard

The minor major seventh is a somewhat unusual chord, but it is used in jazz, in film music, and in some pop songs.

Hitchcock chord

The film music composer Bernard Herrmann used this chord in the scores for the films Vertigo and Psycho, both directed by Alfred Hitchcock. Because of this it is sometimes known as the "Hitchcock chord".

Line cliché

One way that the minor major seventh chord is used in pop and jazz is in a so called line cliché.

A line cliché is a sequence of chords, where either the top or the bottom note moves in semitone steps. An example would be the sequence:

• A minor
• A minor major seventh
• A minor dominant seventh
• A minor sixth

Two examples are:

• the jazz standard My funny valentine (in C)
• the intro to Michelle, by the Beatles (in F)

Movable guitar chords

Here are the shapes of the minor major 7th chord as movable guitar chords with the root on the strings 6, 5 and 4.

Augmented major seventh

An augmented major seventh chord is a combination of an augmented triad, and a major seventh.

This is what a C augmented major seventh (C+Δ7) chord looks like on the piano keyboard

The augmented major seventh chord is used in jazz and in some classical music, but not widely.

Movable guitar chords

Here are the shapes of the augmented major 7th chord as movable guitar chords with the root on the strings 6, 5 and 4.

Augmented triad

To complete our list of chords which can be created by stacking thirds, we have the combination of 3 major thirds.

Since a major third contains 4 semitones, the fourth note is 12 semitones above the root, which makes it the octave of the root.

That means, that the combination of 3 major thirds is not a seventh chord but simply an augmented triad.

Oddball seventh chords

So far, we have discussed seven different 7th chords, all built by stacking minor and major thirds.

There are four more more 7th chords, which don't fit into this schema. These are:

• the augmented 7th or 7th sharp 5
• the 7th flat five
• the 7th suspended 4th
• the diminished major 7th

These are real chords, but they are all unusual and rarely used.

7th sharp five or Augmented 7th

There are two ways of looking at this chord.

• as a dominant 7th chord in which the 5th note has been raised by one semitone,
  chord symbol 7♯5
• as an augmented triad with a dominant 7th note,
  chord symbol +7

The 7♯5 chord is a so called altered chord. This basically means that is a well known chord, in which a note has been moved up or down by one semitone. We will be looking at altered chords more when we discuss extended chords.

This is what a C 7th sharp 5 (C7♯5) or C augmented seventh (C+7) chord looks like on the piano keyboard

Movable guitar chords

Here are the shapes of the 7th sharp 5 or augmented 7th chord as movable guitar chords with the root on the strings 6, 5 and 4.

7th flat five

The 7th flat five chord is another so called altered chord. The description 7th flat five means that is based on a dominant 7th chord, but 5th note has been lowered by one semitone.

The 3rd and 5th notes are only separated by two semitones, which means you cannot build this chord by stacking thirds.

This is what a C 7th flat five chord looks like on the piano keyboard

Movable guitar chords

Here are the shapes of the 7th flat 5 chord as movable guitar chords with the root on the strings 6, 5 and 4.

7th suspended 4th

The 7th suspended 4th chord is a combination of a suspended 4th chord and a seventh note. The separation between the 4th and 5th notes is only two semitones, so you cannot build this chord by stacking thirds.

This is what a C 7th suspended 4th chord looks like on the piano keyboard

Movable guitar chords

Here are the shapes of the 7th suspended 4th chord as movable guitar chords with the root on the strings 6, 5 and 4.

Diminished major 7th

The diminished major 7th chord is a combination of a diminished triad and a major seventh note. The separation between the 5th and the 7th notes is five semitones, so you cannot build this chord by stacking thirds.

This is what a C diminished major 7th chord looks like on the piano keyboard

Here you can see that the separation between the G♭ and the B is five semitones.

Movable guitar chords

Here are the shapes of the diminished major 7th chord as movable guitar chords with the root on the strings 6, 5 and 4.

Shell voicings

A shell voicing is a way to play a chord with some notes missing.

A 7th chord has the chord factors 1-3-5-7. In a shell voicing, you leave out 5th and play only the chord factors 1-3-7.

The 5th is generally considered to be the least important note in a chord. Of all notes in a chord, the 5th sounds most like the root and therefore adds little additional colour to a chord.

Leaving out the 5th is a very common practice in more or less all chords.

This is what a C7 shell voicing would look like on the piano keyboard.

Movable guitar chords

Shell voicings are easy to play on a guitar as movable chords.

Since the voicings only have three notes, we can look at versions with the root on string 3, 4, 5 or 6.

In all cases, the conceptual shape (with the notes in ascending order) is easily playable, so there is no need to look for a playable shape.

As always we will look at the chord with the root on fret 7.

Shell voicings with two notes

You can play even simpler shell voicings with only two notes.

There are two versions:

• the root and the 3rd
• the root and the 7th

These are harmonies that a piano player might play with the left hand, in particular if they are playing a melody with the right hand.