The Relationship Between The Diminished Seventh And The Half-Diminished Seventh Chord

We’ll be looking at the relationship between the diminished seventh and the half-diminished seventh chord.

I’ve come across several musicians who would want to know the difference between the diminished seventh chord and the half diminished seventh chords. Most times, I shy away from discussing this subject because it’s vast.

Today, I’m answering that question. I’ll be showing you the structural and functional differences between the diminished seventh and half-diminished seventh chords.

So let’s get started by looking at the structural similarities and differences between the diminished seventh chord and the half-diminished seventh chord.

Structural Similarity/Difference Between The Diminished Chords

The diminished seventh chord and the half-diminished seventh chord consists of the same triad – the diminished triad.

Here are the B half-diminished seventh:

…chords.

Both of them have the B diminished triad in common.

To the B diminished triad:

…adding an A note:

…produces the B half-diminished seventh chord:

…while adding an Ab note:

…to the B diminished triad:

…produces the B diminished seventh chord:

Let’s go ahead and do a contrast between these two chords related by the diminished triad.

The Scale Degree Position Of The Diminished Chords

The diminished and half-diminished seventh chords are chords of the seventh degree.

Submission: The half diminished seventh chord can also be found on the second degree of the natural minor and harmonic minor scales, however, they don’t have the same harmonic attribute of the diminished chords of the seventh degree (aka – “leading note chords “.) The chords of the seventh degree have what music scholars call the leading note feel, which is the tendency to move towards the first tone of the scale – the tonic.

The diminished seventh chord is the chord of the seventh degree in the minor key, while the half-diminished seventh chord is the chord of the seventh degree in the major key, and both of them are leading note chords (of the seventh degree) that resolve to the tonic triad.

In the keys of C major and minor, diminished chords formed on B (the seventh tone), have the tendency to resolve to C (the first tone).

The Leading Note Chord Of The Minor Key

In the case of the key of C minor:

…we’re using the harmonic minor scale because of the shortcomings of the natural minor scale.

Raising the seventh tone of the C natural minor scale (which is Bb):

…to B:

…produces the C harmonic minor scale:

Forming a chord (using tertian harmony) on the seventh degree of the C harmonic minor scale (which is B):

…just got easier using the pick-skip technique. Here’s how it works…

Pick B:

…skip C and pick D:

…skip Eb and pick F:

…skip G and pick Ab:

The leading note chord of the minor key is the diminished seventh chord. In the key of C minor, the leading note chord is the B diminished seventh chord.

The Leading Note Chord Of The Minor Key

The key of C major, which comprises of all white notes from C to C:

…has B as its seventh degree (aka – “leading note”)

Following the same pick-skip technique of chord formation, we can form its leading note chord.

Pick B:

…skip C and pick D:

…skip E and pick F:

…skip G and pick A:

The half-diminished seventh chord is the chord of the seventh degree of the major key. In this case, we have the B half-diminished seventh chord:

…as the leading note chord in the key of C major.

In a nutshell, the diminished seventh chord is the leading note chord of the minor key, while the half-diminished seventh chord is the leading note chord of the major key.

Resolution Of The Diminished Seventh Chord

Diminished chords are unstable and have the tendency to resolve to a more stable chord. If used as the leading note chord, the diminished chord usually resolves to the tonic triad.

Resolution Of The Half-diminished Seventh Chord

Considering that the half-diminished seventh chord is the leading note chord in the major key, it can be used as a passing chord to major chords.

When you’re given the C# half diminished seventh chord:

…which is a leading note chord to an unknown major chord.

The root of the unknown major chord [that the given half-diminished seventh chord resolves to], is usually a half-step above the root of the given half-diminished seventh chord.

A half-step above C#:

…is D:

Therefore, the C# half-diminished seventh chord:

…resolves to the D major triad.

Conversely, if you’re given the D major triad:

…all you need to do is as simple as determining its leading note and forming a half-diminished seventh chord on the leading note.

Due to the fact that the leading note is always a half step below a given note, the leading note of D is C#:

…and consequently, the C# half-diminished seventh chord:

…would resolve to the D major triad:

Resolution Of The Diminished Seventh Chord

The leading note chord in the minor key is the diminished seventh chord. Considering its affinity for the minor triad, it can be used as a passing chord to minor chords.

“Given the E diminished seventh chord:

…determine the minor chord it’s resolving to.”

The root of the unknown minor chord [that the given diminished seventh chord resolves to], is usually a half-step above the root of the given diminished seventh chord.

A half-step above E:

…is F:

Therefore, the E diminished seventh chord:

…resolves to the F minor triad:

Conversely, if you’re given the F minor triad:

…all you need to do is as simple as determining its leading note and forming a half-diminished seventh chord on the leading note.

Due to the fact that the leading note is always a half step below a given note, the leading note of F:

…is E:

…and consequently, the E diminished seventh chord:

…would resolve to the F minor triad:

Diminished Chords As Upper Structure Chords

The half-diminished and diminished chords can be used as upper structure chords. The term upper structure is used by music scholars to refer to a chord that is played over another chord.

The Dominant Ninth Chord

Over any given note on the keyboard, if you go up a major third and form a half-diminished chord, you’ll form an overall dominant ninth chord. Let me show you how this works.

In the key of G:

…a major third from G is B:

Playing a B half-diminished seventh:

…over G on the bass:

…produces the G dominant ninth chord:

Following the same procedure in other keys would help you form the dominant ninth chord.

The Dominant Seventh [b9] Chord

Forming the diminished seventh chord on the third tone of the major scale of a given key, produces the dominant seventh (flat ninth) chord. Here’s how it works…

The third tone of the C major scale:

…is E:

Playing an E diminished seventh chord:

…over C on the bass:

…produces the C dominant seventh (flat ninth) chord:

Click here to learn more about how four dominant seventh flat ninth chords relate to each other.

In a nutshell, the half-diminished seventh chord is the upper structure chord of the dominant ninth chord while the diminished seventh chord is the upper structure of the dominant seventh flat ninth.

Final Words

Leading note chords are not commonly used because of their inherent degree of dissonance. However, this dissonance can be harnessed and used properly.

The diminished and half-diminished seventh chords are all diminished chords, however, they have structural and functional similarities and differences.

See you in another post!

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Chuku Onyemachi

Head of Education at HearandPlay Music Group

Onyemachi "Onye" Chuku is a Nigerian musicologist, pianist, and author. Inspired by his role model (Jermaine Griggs) who has become his mentor, what he started off as teaching musicians in his Aba-Nigeria neighborhood in April 2005 eventually morphed into an international career that has helped hundreds of thousands of musicians all around the world. Onye lives in Dubai and is currently the Head of Education at HearandPlay Music Group and the music consultant of the Gospel Music Training Center, all in California, USA.

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