Using a Diminished-ii Chord in Major Key Songs

If your song is in a major key, you know that the ii-chord is going to be minor. So if your song is in the key of C major, the chord based on the note D will be Dm (D-F-A). And you’ll be using progressions that might be like the following:

1. C  F  Dm  G  C
2. C  Dm  G  Am
3. Am  F  Dm  G7  C

If you’re looking for a way to branch out and come up with chord progressions that are a little more creative rather than randomly throwing in chords that come from other keys (an improvisatory process that can take a long time to give good results), you might try:

1. choosing one of the chords from a basic progression, and then…
2. keeping the root the same, but changing the quality of the chord (change a major chord to a minor one, let’s say) built on that note.

That’s what’s going on when you substitute the F chord (IV), using Fm (iv) instead. That kind of substitution is called a modal mixture, or a borrowed chord, because the Fm comes from the minor key of C minor. So in that sense, we’re borrowing Fm from the key of C minor.

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There are other chords you can borrow, and one that’s related to that minor iv-chord is the diminished-ii chord. Here’s how it works.

As you hopefully know, take any note that comes from the scale of the major key you’ve chosen, build a 1-3-5 triad on that note, and you’ve got the chord that lives naturally in that key. That means that in C major, the tonic triad — also called the I-chord — is C-E-G. A triad on D is the ii-chord, D-F-A. A triad on E will give us the iii-chord, E-G-B, and so on.

That ii-chord (D-F-A) is minor. It’s minor because minor triads are created by forming a perfect fifth (D to A) and then inserting a minor 3rd above the root (D-F).

But if you change that A to Ab, you get this triad: D-F-Ab. That triad is a diminished triad, because diminished triads are created by forming a diminished fifth (D to Ab) and then inserting a minor 3rd above the root (D-F).

How to Use the Diminished-ii-Chord

You’ll be pleased to know that the diminished-ii chord (iiº) can be used practically anywhere a minor ii-chord might be used. So if you look at those 3 sample progressions near the start of this post and change the Dm chords to Dº, you’ll get these:

1. C  F  Dº  G  C
2. C  Dº  G  Am
3. Am  F  Dº  G7  C

Earlier I said that the Dº is closely related to the minor iv-chord. Here’s how: In C major, the minor iv-chord uses the notes F-Ab-C. The iiº uses two of those notes, the F and Ab. In fact, playing the iv-chord but using D as your bass note will give you iiº7: D-F-Ab-C.

So the iiº in those 3 progressions above will also sound great when you use the minor iv-chord instead (C  F  Fm  G  C).

It’s not an overly-used chord in pop genres. It was quite popular in slower ballads, like “Afterglow” by Genesis, the intro for which used the progression G  Gmaj7  C  Aº  G… an Aº when we were expecting Am.

The best way to be sure you’re using it in a way that makes tonal sense is to write out some standard major key progressions, and then replace any ii-chord or IV-chord with iiº.

Written by Gary Ewer. Follow Gary on Twitter

“How to Harmonize a Melody” shows you the steps to adding chords to that melody you’ve just come up with. With sound samples to help you understand the concepts.