Are Diminished Triads Simply Rootless Dominant Seventh Chords?

Our focus in this lesson is on diminished triads and their relationship with dominant seventh chords.

A vast majority of beginners and intermediate players know the diminished triad and the dominant seventh chord as two unique chords but this lesson will show you the relationship between both chords.

Let’s get started by refreshing our minds on the dominant seventh chord.

A Short Note On The Dominant Seventh Chord

There are eight tones in the major scale, and each of them has its technical name:

The first tone of the scale is the tonic.

The second tone of the scale is the supertonic.

The third tone of the scale is the mediant.

The fourth tone of the scale is the subdominant.

The fifth tone of the scale is the dominant.

The sixth tone of the scale is the submediant.

The seventh tone of the scale is the subtonic.

The eighth tone of the scale is the octave.

The term “dominant” is associated with the fifth tone of the scale. So, in the key of C major:

…the fifth tone (which is G):

…is the dominant.

“Here’s The Dominant Seventh Chord…”

The dominant seventh chord is “the seventh chord of the fifth tone of the scale” which is also known as the 5-chord (for those of you who are familiar with the number system.

So, forming a seventh chord on G:

…encompassing a seventh (from G to F):

…produces the G dominant seventh chord:

…which is formed by stacking notes together in third intervals:

G-B (third interval):

B-D (third interval):

D-F (third interval):

“What Are Diminished Triads?”

There are seven triads in the major key and they are collectively referred to as scale tone chords. In the key of C major:

…here are the scale tone chords:

The 1-chord:

The 2-chord:

The 3-chord:

The 4-chord:

The 5-chord:

The 6-chord:

The 7-chord:

The diminished triad is the chord of the seventh tone of the scale (aka – “the 7-chord”). For example, in the key of C major:

…the 7-chord:

…is a diminished triad.

Recommended: The Diminished Triad

Attention: To learn more about this, I recommend our 500+ page course: The “Official Guide To Piano Playing.” Click here for more information.

The Relationship Between The 5-chord And The 7-chord

In this segment, we’ll be answering the question below:

Are diminished triads simply rootless dominant seventh chords?

However, there are important things the dominant seventh chord and the diminished triad have in common and it’s important for us to take a look at them before we come to a conclusion.

Diminished Triads Vs Dominant Seventh Chords

From what we’ve covered in this lesson so far, the dominant seventh chord is the 5-chord while the diminished seventh chord is the 7-chord.

“So, What’s The Relationship Between The 5-Chord And The 7-Chord?”

In the key of C major:

A closer look at the 5-chord (a dominant seventh chord):

…and the 7-chord (a diminished triad):

…shows that they have something in common.

The tones of the diminished triad (the 7-chord):

B, D, and F

…are in the dominant seventh chord (the 5-chord):

G, B, D, and F

Attention: 75% of the tones of the dominant seventh chord are identical with the tones of the diminished triad.

If three out of the four tones of the dominant seventh chord are identical to the tones of the diminished triad, then it’s not wrong to substitute one for the other or possible to overlook the relationship between them.

Every dominant seventh chord has its corresponding diminished triad. For example, the A dominant seventh chord:

…is related to the C# diminished triad:

The E diminished triad:

…is related to the the C dominant seventh chord:

So, every dominant seventh chord (5-chord) is related to a given diminished triad (7-chord).

The Rootless Dominant Seventh Chord

The rootless voicing concept has to do with playing a chord without its root. The dominant seventh chord can be played using the rootless voicing concept.

The root of the G dominant seventh chord:

…is G:

Playing the G dominant seventh chord without its root note produces “B-D-F”:

…which is for all intents and purposes a B diminished triad.

Attention: To learn more about this, I recommend our 500+ page course: The “Official Guide To Piano Playing.” Click here for more information.