Diminished, Augmented & Seventh Chords: Learn Them Here!

In our blog explaining how chords work, we already touched on the diminished, augmented, and seventh chords. Here, we dive a little deeper into the inner workings of these chords and their function, covering everything from a normal seventh chord (the dominant seventh), to minor sevenths and major sevenths, and the difference between a diminished and half-diminished chord. We’ll also explain terms like ‘diatonic’, ‘modal’, and ‘enharmonic’, setting you up with a bank of knowledge to help you get writing.

An Overview of Intervals
The Dominant Seventh (7)
Diatonic & Modal
The Major Seventh (maj7, ∆)
The Minor Seventh (m7, min7, mi7)
Diatonic Sevenths
Diminished Chords
The Diminished Triad (mb5, dim, or °)
The Diminished Seventh Chord (dim7 or °7)
Enharmonic Notes
The Half Diminished Seventh (m7b5, ø or ø7)
The Augmented Chord (+, #5 or Aug)
Recognisable
Things Worth Knowing
Guitar Tricks
Leave it Out
An Overview of Diatonic Seventh Chords
Overview of (Half) Diminished & Augmented Chords
See Also…

An Overview of Intervals

Since intervals will come up a lot in this blog, we’ve included an overview of them below. Click on the image to enlarge it.

The intervals, counted from C. 1 = major second, 2 = major third, 3 = perfect fourth, 4 = perfect fifth, 5 = major sixth, 6 = major seventh, 7 = octave, 8 = major ninth, 9 = augmented second, 10 = augmented fourth, 11 = augmented fifth, 12 = augmented sixth, 13 = minor second, 14 = minor third, 15 = minor fifth, 16 = minor sixth, 17 = minor seventh.

The Dominant Seventh (7)

First, we return to the ‘normal’ seventh chord that we covered in our previous blog. This is more commonly referred to as a dominant seventh chord, which can be notated as C7, D7, E7, and so on, but is usually just called a seventh (C seventh or C seven). The dominant seventh chord is a major chord with a minor seventh added onto it (see the image of the piano keys above). So, a C7 is made up of C, E, G, and Bb, where the Bb is our added seventh. It’s that simple.

Every major key has just one scale-specific dominant seventh chord. These are also known as diatonic chords, meaning that the notes that make up the chord all match the notes of the corresponding scale. The diatonic dominant seventh chord always falls on the fifth interval of the major scale. So, if we look at the C-major scale (C, D, E, F, G, A, B, C), the dominant seventh chord is G7 – G, B, D, F – where every note is part of the C-major scale.

In our blog about chord progressions, we explained why a dominant seventh chord always feels like it wants to ‘resolve’ into what we referred to as the ‘home’ chord – or the root of the scale in which the chord progression is written. As such, the G7 (G, B, D, F) will always want to resolve into the C-major (C, E, G). This is because of the leading notes that form part of the G7, so the leading note B will always have the urge to return back to the C, and the F will always want to return to the E of the C-major chord.

As we’ve already mentioned, the C7 chord includes a Bb, which doesn’t appear in the C-major scale, making C7 a ‘modal’ chord (or ‘borrowed chord’) within the C-major key. While you can still use the chord, this is a detail worth knowing.

The Major Seventh (maj7, ∆)

The name ‘major seventh’ is initially confusing, but these are major chords with an added augmented seventh. So here, the term ‘major’ refers to the added seventh, and is notated as (in the case of C) Cmaj7 or ∆ – C, E, G, B. If we compare it to the dominant seventh chord (so C7, or C, E, G, Bb), the difference lies in the B (the major seventh) and the Bb (the minor seventh).

Have another look at the piano keys above. In terms of timbre, the major seventh chord is different from the dominant seventh chord, and the dominant seventh will always want to return to the home chord of its key. So, C7 wants to resolve to F-major. The augmented sevenths of the major seventh chord have more colour than a major chord but have much less ‘urge to resolve’ than the dominant seventh chord. A major seventh chord can lend a piece a jazzy character, so you can’t use them everywhere, but of course, this depends on the style of piece or song you’re working on. The minor seventh chord is a gorgeous chord, but usually works best when used sparingly.

The Minor Seventh (m7, min7, mi7)

Now we come to the minor seventh chord, which is notated as Cmin7, Cmi7, or more commonly Cm7. The ‘minor’ of the minor seventh chord has no relation to the seventh, but refers to the minor third of the chord, because the minor seventh is a minor chord with a minor seventh added on. Cm7 is made up of C, Eb, g, Bb, where Eb is the minor third, and Bb is the minor seventh. The character of the minor seventh chord has a very similar quality to the major seventh chord and what might be described as a ‘basic’ colour since it has no strong urge to resolve. Just like the major seventh chord, the minor seventh chord has a jazz flavour to it, so neither the major or minor seventh chords are used all that much in rock music.

Diatonic Sevenths

In the key of C, the C-major chord is a ‘diatonic’ chord, since the notes that make up the C-major chord (C, E, G, B) are all part of the C-major scale. The C-major key includes three diatonic chords: C, F, and G. Two of these chords are also diatonic major seventh chords: Cmaj7 and Fmaj7. The diatonic seventh chord of G is G7, so the dominant seventh chord that we covered earlier. The C-major scale also includes three minor chords: Dm, Em, and Am. The minor seventh of each of these chords is diatonic, so the notes that make up Dm7, Em7 and Am7 can all be found in the C-major scale.

To summarise: the diatonic seventh chords of C-major are Cmaj7, Dm7, Em7, Fmaj7, G7 and Am7. This just leaves the B-chord. But why? The C-major B-chord is built out of notes B, D, and F: which stacks two minor thirds. This is referred to as a diminished triad, or the Bmb5 chord (or B minor flat 5), which we’ll talk more about in a bit. The third in this chord is a minor third (just like a minor chord) and the fifth is a diminished fifth. The notes B, D, and F that build the Bmin5 chord all belong to the C-major scale, so Bmb5 is a diatonic chord of C-major.

So, how can we stick a seventh onto the Bmin5 that fits in the C-major key? For this, we need the minor seventh of the B, which is A. So, the chord is turned into B, D, F, A, or Bm7b5 (B minor 7 flat 5). Another name for this special chord is B half-diminished, which brings us to the next section of this blog: the diminished and half-diminished chords.

Diminished Chords

The chords that we’ve looked at are all diatonic chords. In other words, they are chords built of notes found in one specific major or minor scale. Now we step into the realm of chords that aren’t necessarily diatonic: the diminished triads, the diminished sevenths, the half-diminished, and the augmented chords. These are all tension-ridden chords that want to resolve, and this is exactly why they’re often used as transition chords: chords used to move smoothly to a different chord or a different key.

The Diminished Triad (mb5, dim, or °)

First we come to the diminished triad. We’ve already briefly mentioned this chord when talking about the Bmb5 chord. The diminished triad is a stack of two minor thirds. As we’ve said already, the third interval in this chord is a minor third (just like with a minor chord) and the fifth is a diminished fifth. The C diminished triad is therefore C, Eb, Gb. You can notate the diminished triad in two different ways: Cmb5 or Cdim.

The Diminished Seventh Chord (dim7 or °7)

You can expand the diminished triad (a stacking of two minor thirds) to make a quadrad chord made up of a stack of three minor thirds; otherwise known as a diminished seventh chord. So the C diminished seventh then becomes C, Eb, Gb, A (see the paragraph below!). This is notated as Cdim7 or °7, and is a chord that often serves as a transition between other chords. For example, it can be used to get from the fourth interval back to the first interval, like in the classic blues progression: F7, F#dim7, C7.

Cdim7 (C, Eb, Gb, A) is also built of the same notes as D#-Ebdim7, F#-Gbdim7 and Adim7. The same applies for C#dim7 (C#, E, G, A#), Edim7, Gdim7 and A#-Bbdim7. And for Ddim7 (D, F, Ab, B), Fdim7, G#-Abdim7 and Bdim7. In other words, with three different note combinations, we can build every diminished seventh chord.

Enharmonic Notes

So, we’ve already explained that the C diminished seventh chord is made up of notes C, Eb, Gb, and A, but… this is a simplified notation. The theoretical notation is actually C, Eb, Gb, and Bbb, where that Bbb is actually the same note as A – because these two notes are ‘enharmonically’ alike. So, why is it notated like this? Well, in our very first blog about chords, we learned that we always count in semitones from the root note, and that the seventh (whether major, minor, or diminished) is always the seventh semitone (the letter used to indicate the note) from the root note. For example: you want to play a C7 chord, or in other words, a major chord with a minor seventh added on. By counting seven semitones or letters from C – the root note of the chord (see the piano keys above) – you’ll land on a B. Stepping from a C to a B is a major seventh interval, so we diminish or lower the B by a semitone to the minor seventh: Bb. But, we’ve just learned that there’s also such a thing as a diminished seventh, which we get by lowering the B by another semitone to get Bbb, which, in practice, is the same note as A. The letter ‘B’ is still used here because the note has the function of a seventh (the seventh letter, or interval) and not of a sixth (the sixth letter or interval).

The Half Diminished Seventh (m7b5, ø or ø7)

We briefly encountered the half diminished chords when talking about minor seventh chords. The half diminished chord uses almost exactly the same notes as the minor seventh chord, but then with a diminished fifth. C half diminished is made up of C, Eb, Gb, and Bb. Why is this chord half diminished? We can find out by comparing it to the diminished seventh chord. The C diminished seventh is C, Bb, Gb, and A (or, as we just found out, C, Eb, Gb, and Bbb). A diminished seventh chord is built by stacking three minor thirds. A half diminished seventh chord is built by stacking two minor thirds and a major third. Just like the diminished seventh chord, the half diminished chord is often used as a transition chord, but has a less dense and heavy sound to it than a diminished seventh chord.

Diminished seventh chords are not specific to any major key (are not diatonic). This is also the case for most half diminished chords, with the exception of the half diminished chord on the seventh step. In C-major, the B half diminished chord (B, D, F, and A) is a diatonic chord. A half diminished chord can be notated in a number of ways but is generally notated as a minor seventh chord with a diminished fifth, giving us Cm7b5 (spoken aloud as C minor 7 flat 5). An easier way of writing it down is ‘Cø’ or ‘Cø7’. This is similar to the shorthand notation of a diminished triad (C°), but then the ‘o’ is struck through. To summarise: C° is the diminished triad (C, Eb, Gb), C°7 is the diminished seventh chord (C, Eb, Gb, A), and Cø or Cø7 is the half diminished chord (C, Eb, Gb, Gb).

The Augmented Chord (+, #5 or Aug)

So, we’ve covered the diminished and half diminished chords, and to finish, we’ll take a look at augmented chords, which can be notated in a number of different ways. You can notate an augmented C chord as C+, C#5 or Caug. The augmented chord differs from the major chord because it has an augmented (or raised) fifth. For example: C-major is C, E, G, while Caug is C, E, G♯. Just like the diminished chord, the augmented chord feels like it has an urge to resolve – like it wants to move on, so is also often used as a transition chord – between the first step and the fourth step, for example. In slow blues, you’ll often hear the chord progression A7, A7+, and D7 where the A7 is played for three counts, A7+ is played for one count, and then D7 is played for a full four counts. In this example, a minor seventh has been added to the augmented chord, giving us A augmented seventh: A, C♯, F, G, which gives the chord more weight and an even greater urge to resolve. In blues in general, this kind of seventh is almost always played.

Recognisable

The chords we’ve covered in this blog all have an immediately recognisable feel to them. With practice, you’ll be able to pick them out straight away. You’ll start to hear that the diminished and augmented chords move outside of the key so you can easily recognise them, while the half diminished chords will take a little longer to jump out. But these chords aren’t so commonly used in pop music.

This blog, alongside our blog about the basics, gives you a solid foundation in chord theory and covers all of the most essential chords when it comes to blues, pop, and rock. You can already do a lot with what we’ve covered, but naturally, there are plenty more chords out there. In our following blog, we cover the chords that are most used in jazz as well as some pop and blues: the 9th, 11th, and 13th chords, and how they’re put together.

Things Worth Knowing

Guitar Tricks

It’s worth having a kind of automatic knowledge of major and minor chords and their corresponding seventh chords, so you can play them without having to think about it. This is definitely possible with diminished and augmented chords as well. However, half-diminished chords can be a little more tricky, but there is one little ‘hack’ you can learn to make life easier – certainly if your go-to instrument is the guitar:

Say you want to play a half-diminished D (Dø or Dm7b5). Instead of playing the full chord straight away, play the normal Fm. Since Dø is built out of D, F, Ab, and C, and Fm is built out of F, Ab, and C, it has the same notes as Dø, but without the D. If you’re a guitarist, missing out the D isn’t going to be such a big deal. The D is the root note, and the bassist and maybe the keyboard player will usually play the D. It’s always better to just leave a note out than play the wrong note or have to pause to remember or figure out what the chord looks like. In fact, it can actually work in favour of the song or piece of music if not every musician plays every note of the same chord at the same time. Sharing the notes out across the members of the band or ensemble gives the notes more room to breathe and can really add something. Find out more about the effect of leaving notes out below.

Leave it Out

If you’re a guitarist or a pianist, then you can get away with just playing the thirds of chords. The third is important, because it’s this bit of a chord that determines whether it’s major or minor. This doesn’t apply to power chords, since these are made up of the root note and the fifth, so there is no third. But, if it’s a chord with a minor seventh, that will need playing too, because the third and minor seventh are the most essential ‘colours’ of the chord. Of course, the root note is also important, but this is usually played by the bass. On a piano, it can be quite nice to play a chord without the root note. It can leave the sound more open. But what about the fifth? If it’s a perfect fifth, which it will be with most chords, then you can leave it out without worrying about it too much. This is especially true for pianists. The perfect fifth (or dominant) is strongly related to the root note (the tonic) and actually does very little to the colour of the chord. This naturally changes as soon as you raise or lower the perfect fifth – then it suddenly becomes a very decisive part of the chord and should definitely be played. If you have a keyboard player and guitarist in the band, then they could decide that the guitarist just plays the basic chords – so goes no further than the seventh, while the keyboard player colours the chords in by playing the notes that go further than the seventh (so the 9th, 11th, and 13th). These chords will be covered in more detail in our next blog.

Functional Harmonic or Just Colour

Most chords will have a harmonic function, meaning that they have a strong urge to resolve into the following chord. But that isn’t always the case, and it’s definitely not the case for more special chords. Try playing an augmented chord and adding a major seventh to it. So, for example, C, E, G♯, B – or C+maj7. While it might sound a little strange, the tension in this chord is pretty intense. But which chord does it want to resolve into? It’s actually unclear. Such a chord is perfect for creating tension in film soundtracks since it can really stand alone. Also, the seventh in many blues chords adds more colour rather than serving a harmonic function.

An Overview of Diatonic Seventh Chords

In the table included below, you can see the diatonic seventh chords listed per major key (to fully understand this, read the blog above). Cmaj7 (C∆) is made up of C, E, G, and B. Cm7 is made up of C, Eb, G, and Bb, and so on. The Roman numerals included above the table indicate the intervals. The chord on the seventh interval is a half diminished chord and looks a lot like a minor seventh chord, but then with a diminished fifth added on (minor 7 flat 5). This chord can be noted in one of two ways: Bm7b5 and Bø. Click on the image to enlarge it.

Overview of (Half) Diminished & Augmented Chords

In the table included below, you can see the diminished seventh chord; half diminished chord; and augmented chord listed per key. In C, the notation for the diminished triad is: Cmb5 or C°. The notation of the diminished seventh chord is: Cdim7 or C°7. The notation for the half diminished chord is Cm7b5, Cø or Cø7. And the notation for the augmented chord is C+, C#5 or Caug.

We have kept the names of the chords simple to make life a little easier. For example, the E of the diminished Db chord should actually be an Fb. This is because of the enharmonically alike notes we discussed earlier, and in the key of Db, there’s actually a diminished F, so an Fb. So, we’ve left out some details that are less important and opted for simple and practical chord names. Click on the image to enlarge it.