A great tool for adding a different color in a chord progression is to include one or more half-diminished seventh chords (sometimes just called half-diminished chords).
I’m going to save you too much detailed theory on how diminished chords work – though there’s more if you’re interested here and here – but here’s a rundown of the essentials:
First off, you probably remember when I said that chord on VII of the scale is a diminished chord. That’s because – unlike in major and minor chords – there are only six half steps from the bottom note to the top:
(Count them if you don’t believe me. Or just play the chord and you’ll hear how it sounds totally different to a major or minor chord.)
In a lot of classical music, it’s common to find what’s called a diminished seventh by adding the seventh three half steps above the top note – in this case, A flat – though this chord is rarer in popular genres.
Instead, in popular music it’s much more common to find a chord called a half-diminished seventh, which has a seventh added on the note four half steps above the top note – in this case, A – like this:
You’ll often find half-diminished chords written in shorthand either as Bø – that’s a B and a slashed circle, not ‘Bø’, a wardrobe from Ikea – or as Bmin7b5 or Bm7(b5), which you can pronounce ‘B minor seventh flat fifth’ (or just, as you know, ‘B half diminished’).
So that’s the theory in a nutshell: a half-diminished seventh chord is a regular diminished chord with a seventh that’s a whole step below the root added.
There are a handful of different things you can do with this chord, but we’re going to focus on three types of progression – two in major keys and one in minor keys – that you should know about.
In major keys, the first type of progression uses the half-diminished seventh chord on the seventh degree of the scale. You can put all kinds of chord before the half-diminished seventh chord, but pretty much only one chord after it: the major chord a fifth below. Here’s a great example:
If you do the math, you’ll realize the B–E–A root motion makes it a cycle of fifths progression, which is why it works so well.
And of course – before you get ahead of me – I’m not saying the only chord that can follow vii7b5 is III, but in twenty years of writing songs it’s the only one I’ve found that’s always effective. (If you find any others, you should not only let me know, but also one of the Nobel Prize committees, because you’ve just discovered something really awesome.)
The second type of major-key progression uses the half-diminished seventh chord on the sharpened fourth degree of the scale: that is, the fourth degree of the scale but one half step higher.
One common way to use this chord is as a ‘passing’ chord in between chords IV and V, like this:
Or even like this:
You’ll notice it’s a much more versatile chord than the half diminished seventh on the seventh degree of the scale – you have a lot more options for how you can use it effectively – but, that said, it tends to be most effective when it’s followed by either chords IV or V. (Though there are exceptions. You don’t have to @ me on Twitter to tell me that.)
On top of that, I’ll just add that the chord also works well when it comes after chord vi:
Or, if you want something really bold, after a big jump in the bass from chord I:
Finally, the third type of progression – the one in minor keys – might look kind of similar to the first:
I’m talking about that ii7b5–V progression, especially when followed by I – the one that’s exactly the same as vii7b5–III–vi in major keys, except because a major key’s relative minor is chord vi, in this case the numbering is different.
Anyway, this is a really strong progression – again because it’s based on the cycle of fifths – and again because the use of that half-diminished color really makes the progression interesting.
You can also do something like this, which extends the cycle of fifths back one extra chord to chord VI, and includes the kind of big bass jump onto the half-diminished seventh chord we saw in the second type of progression I told you about:
As usual, my list of three types of half-diminished seventh progressions isn’t a complete list of half-diminished seventh progressions. But they are three flavors of very effective chord sequences that are definitely worth getting to grips with if you want to throw a couple of half-diminished seventh chords in your next song.
If you are interested in viewing some of Ed’s other articles in this series, please click one of the following links: inversions, pedal notes, chromatic alterations, chord extensions, suspended fourth chords, 8-bar or 16-bar progressions.