• # Chromatic Dissonance: Chord Formation Using the “Tritone”

Intervals are used as building blocks in chord formation. This makes them harmonic devices.

In a previous post, we explored chromatic dissonant intervals (augmented fourths and diminished fifths) and their relationship by inversion.

An augmented fourth and a diminished fifth are closely related, but in terms of usage, we tend to use the diminished fifth as opposed to the augmented fourth.

In this article, you’ll learn why this is the case in chord formation.

## TERTIAN HARMONY

The notes of a chord are called chord tones. It’s common to see these chord tones stacked in thirds. This is because in traditional practice, thirds are used to create harmony. This harmony in thirds is called tertian harmony.

If we select thirds from the major scale of C, starting from C, we’ll create a triad:

The triad is built off the first, third and FIFTH degrees of the scale. Notice, you have a fifth in the chord already. You may have observed that we skipped the fourth (it’s clearly in between the third and the fifth):

In terms of chord construction using tertian harmony, there’s an occurrence of the fifth before the fourth. However, we’ll still find the fourth useful in minor eleventh chords:

…suspended chords:

…and quartal chords:

Therefore, we’ll be concerned with fifths (and not fourths) because of their occurrence and importance in tertian harmony (especially in triads).

However, you must also keep it in mind that every fifth has the potential of becoming a fourth. This potential can only be tapped into by inverting the fifth. If we invert triads, we can clearly see fourths.

Root Position – All Thirds

First Inversion – Fourth between G and C

Second Inversion – Fourth between G and C

## DIMINISHED FIFTHS

In chromatic dissonant intervals, the quality of fifth is the diminished fifth. We talked about its tension, instability and tendency to resolve and also compared it with the universal consonance – perfect fifth. Let’s get into the formation of diminished fifth intervals.

### Formation

There are so many perspectives to the formation of diminished fifth intervals. The easiest is the interval shrinking technique.

The interval shrinking technique helps us reduce the size of an interval by raising the lower note or lowering the higher note using a given melodic progression. This technique helps us derive an interval from a closely related interval we’re familiar with.

The closest fifth we are familiar with is the perfect fifth. (We covered the perfect fifth in an earlier post where we gave out a free 111-pg guide on Consonant Intervals).

Let’s look at the two approaches to the interval shrinking technique.

Approach #1Raising the lower note.

Using a perfect fifth on C:

…raising the lower note will yield C♯-G.

Here, we have an interval that is less than a perfect fifth – a diminished fifth.

Approach #2Lowering the higher note.

Using a perfect fifth on C:

…lowering the higher note will yield C-G♭.

Here, we have another diminished fifth interval.

The interval shrinking technique can also yield an augmented fourth. These intervals are NOT Diminished fifths, even though they sound the same. “There,” “their,” and “they’re” all sound the same but are different words. The same is true here.

Using the first approach, we can raise the lower note to yield D♭-G

Using the second approach, we can lower the higher note to yield C-F♯

There are musical similarities between the diminished fifth and the augmented fourth. If you want to know the similarities and differences between these intervals, I recommend our study guide, HearandPlay 130 – Intervals for you.

## Interval Shrinking Technique

It’s great for you to have more than one way of shrinking the perfect fifth to derive the diminished fifth. However, we’ll stick to one approach and I’ll tell you why.

The first approach gave us a C♯ diminished fifth interval.

The second approach yielded a C diminished fifth Interval.

The two approaches will shrink an octave and give us a diminished fifth. However, the second approach is better because it gives us a diminished fifth on the given key (C) as opposed to the first approach that gives us a diminished fifth, on a different key (C♯). Therefore, we’ll shrink the perfect fifth in this article by lowering the higher note (using the second approach).

We can derive the diminished fifth in all 12 keys using the interval shrinking technique. It’s easier than it sounds.

As you now know, shrinking of the perfect fifth by a semitone progression (or half step) yields a diminished fifth interval.

Therefore, C Diminished Fifth interval is as easy as shrinking a perfect fifth on C by a semitone progression.

C♯ Diminished Fifth interval is as easy as shrinking a Perfect fifth on C# by a semitone progression.

D Diminished Fifth interval is as easy as shrinking a perfect fifth on D by a semitone progression.

D♯ Diminished Fifth interval is as easy as shrinking a Perfect fifth on D# by a semitone progression.

If we go on and on, we’ll have Diminished Fifth intervals in ALL keys with little or no effort.

## APPLICATION IN CHORD FORMATION

The diminished fifth is the building block (aka – “intervallic component”) of several chords. The diminished fifth is also associated with the tritone. Therefore, chords that have the diminished fifth interval are known as tritonic chords.

Tritonic chords are also known as discords because they inherit instability, tension, unpleasantness and the tendency to resolve from the diminished fifth (dissonant interval). Let’s explore discords.

The diminished triad is the only quality of triad in tertian harmony that has a diminished fifth. As a result of that, it’s harmonically unstable. It is naturally the 7th scale degree chord in the major key. The C diminished triad below is the 7th scale degree chord of D♭ major.

The C diminished triad can be broken down into two intervallic components.

Minor third  (C-E♭)

Diminished fifth (C-G♭)

A diminished triad, if broken down into intervallic components, looks like this:

Root + Minor third + Diminished 5th

### Dominant Seventh Chord

The Dominant Seventh chord is the most important tritonic chord. It has the tendency to move towards any note a fifth below or a fourth above. This is the most powerful gravity in music. Dominant seventh chords can be formed by adding a major third below a diminished triad.

If a major third interval is added below the root of a diminished triad, a dominant 7th chord will be formed.

For example, consider a C diminished triad:

Adding an A♭ note below it (which is a major third) will yield an A♭ dominant seventh chord.

If we switch perspectives, we can say that the dominant seventh chord can be formed by building a third degree diminished triad over the root of a given note. Let’s take three examples.

Example 1 – Formation of C dominant seventh

The third degree of C is E.

Therefore, E diminished over C on the bass:

…will yield a C dominant seventh chord:

Example 2 – Formation of E dominant seventh

The third degree of E is G.

Therefore, G diminished over E on the bass:

…will yield an E dominant seventh chord:

Example 3 – Formation of G dominant seventh

The third degree of G is B.

Therefore, B diminished over G on the bass:

…will yield a G dominant seventh chord:

Using the same process, you can form dominant seventh chords in ALL 12 keys.

## Final Words

You’ve taken your knowledge of chromatic dissonant intervals to the next level by learning how to feature them in chord formations. Not only that, but you’ve learned how to easily form dominant seventh chords in any key.

In a future post, we’ll cover other tritonic chords that can be formed from the diminished triad ranging from seventh chords (half-diminished seventh, diminished seventh, diminished major seventh, etc) to sixth chords (minor sixth), and more. See you then!

P.S.

We’ve finally come out with a comprehensive guide that will show you top secrets on chord formation. It will cover triads, sevenths, and extended chords. Inversion of chords using both choral and keyboard styles to enable you to come up with countless permutations is covered for the first time ever. Voicing and Voicing Techniques with dozens of voicing formulas is a major part of this course. Early next year, we’ll be introducing it to everyone who signs up on our early bird notification list. Click here to sign up and let us know you’re interested.

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#### Chuku Onyemachi

Head of Education at HearandPlay Music Group
Onyemachi "Onye" Chuku (aka - "Dr. Pokey") 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.