What Is Tritone Substitution And How To Use It

If the dominant 7th chord is not your favorite 4-note chord, this article should give you a reason to make it so. That's because of tritone substitution. It is a method of replacing a Dom7 chord with another Dom7 chord that shares the same tritone, and it sounds terrific.

Let's first see how it works and then how to use tritone substitution in a chord progression.

What is tritone substitution?

A dom7 chord's tension could be attributed to its tritone.

For example:

G7: G B D F.

Here, B is the 3rd of the chord and F is the ♭7th. The interval between B and F is a tritone (diminished 5th).

We know that the tritone is a symmetric interval. It has the same number of semitones (6) no matter which note comes first.

So if we reverse the notes of this interval from B-F to F-B, it will become a part of some other dom7 chord.

However, the interval between the 3rd and 7th in a 4-note chord is supposed to be some kind of a 5th. Right now, F-B is considered an Augmented 4th. This is easily fixed by renaming B to C♭.

Now consider F to be the 3rd and C♭ to be the ♭7th from the root of that new chord. The root that fulfills that requirement is D♭.

Therefore, the resulting tritone substitute of G7 is D♭7.

D♭7: D♭ F A♭ C♭

As the name implies it is a substitute for the G7 chord since it has a similar kind of tension because of the same tritone. That means they can both resolve to each other's relative I chord.

It is notated as Sub V7.

Tritone substitutes share the same tritone

There is a much shorter way of finding the tritone sub, but I have covered it later here to avoid confusion right now.

Using this substitution leads to an interesting resolution in a chord progression. Let's look at that.

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Analyzing the tritone substitute

Have you ever wondered why the V7-I or the V7-i resolution sounds so good?

Well, let's see why that is.

Take V7 - I progression in the key of C major for example. The chords are G7 and C.

G7: G B D F

C: C E G

Listen to this chord movement V7-I:

When G7 goes to C major, two things happen that give it a satisfying sound:

1. The tritone resolves inwards from B and F to C and E.

2. B is moving to C, which is the 7-1 movement in the scale.

Internal workings of V7-I Progression

From the previous example, we already know that the tritone substitute of G7 is D♭7

Here's the D♭7 - C progression.

The notes of D♭7 are D♭ - F - A♭ - C♭.

As you can see, this chord is not diatonic to the C major scale, but it is just as satisfying as the V7-I progression, probably more so because it is such a breath of fresh air.

Listen to this progression where first I have played it normally, and then used the tritone substitution to spice it up a bit.

I - IV - V7 - I

I - IV - SubV7 - I

So, let's see what is happening inside this progression with the notes.

D♭7: D♭ F A♭ C♭

C: C E G

1. The tritone F-C♭ is resolving outwards to E and C

2. C♭ is going up by a semitone to C, which is the 7-1 movement in scale.

3. The root of D♭7 is coming down by a semitone to the root of C.

Tritone Sub Resolving To Tonic (D♭7 to C Major)

And there we have the secret sauce. In addition to everything that the V7 chord has, its tritone substitute also has a chromatic root movement, which brings a new flavor to the sound.

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How to find tritone substitute quickly

Before we move on to learning different uses, we need to be able to figure out the substitute chord quickly.

Take A7 for example, and let's first find its substitute using the long method and then the shorter way.

Try finding it for yourself before opening this to see the answer.

The notes of A7 are A C♯ E G The tritone here is C♯ - G. Reversing that interval gives us G - C#, and the enharmonic equivalent of C# is D♭. So, renaming C♯ to D♭, the interval becomes G - D♭. Now, consider G to be the 3rd of the new chord and D♭ to be the ♭7th. The chord we get is E♭7.

So, the tritone substitute of A7 is E♭7.

A7: A - C♯ - E - G

E♭7: E♭ - G - B♭ - D♭

Now, notice the relation between the roots of those chords. A and E♭ are a tritone apart from each other.

That makes our job much easier.

To find the tritone substitute of a dom7 chord, just find the tritone interval from the root, and form another dom7 chord on that note.

This is often the source of confusion as well because one might think it is called a "tritone substitute" because the roots are a tritone apart. However, that is just the effect and not the cause in this case.

Now that we can do this quickly, let's learn a few ways to use this progression.

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Using Tritone Substitute in chord progressions

Here are the most common ways tritone substitutes are used.

Tritone Substitutes in secondary dominants

We have seen how we can substitute the V7 chord in a scale already.

However, you can also use tritone subs with secondary dominant chords. Let's take the following chord progression for example:

CΔ7 - A7 - Dm - F - G7 - C

​IΔ7 - V7/ii - ii - IV - V7 - I

CΔ7 - E♭7 - Dm - F - G7 - C

​IΔ7 - SubV7/ii - ii - IV - V7 - I

In the first audio clip, I used a secondary dominant in the progression to target the ii chord. Then I replaced it with its tritone substitute in the second clip.

Notice that in the second progression, the substitute chord (E♭7) was a half-step above the root of the target chord (Dm)

This can be a quick way of finding tritone subs on the fly.

Whenever you want to create temporary tension in a progression, you can use a dom7 chord built on the note that is a half-step above the root of the target chord. This is its Sub V7.

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Tritone Substitute in 2-5-1 progression

ii-V-I is a staple of jazz music, and as you can guess by looking at it, having the V-I in that gives us the opportunity to use tritone substitution.

In the key of F major, ii-V7-I progression would be Gm - C7- F.

The tritone sub of C7 is G♭7.

Replacing it in the progression, we have Gm - G♭7 - F.

Here, notice the beautiful chromatic movement of the roots. That makes it my favorite way of using the tritone substitute.

If you liked that sound, check out my post on other ways of using non-diatonic chords to spice up your chord progressions.

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Tritone Substitute in Secondary 2-5-1

We can combine the last two methods of using tritone subs into one.

Let's learn this with the following chord progression:

I - ii - V - vi

In the key of B♭, this progression would be B♭ - Cm - F - Gm

Here, I want to target the ii chord, which is Cm.

To do so, I am going to be using the concept of secondary 2-5-1, which means I will treat Cm as the temporary i chord, and play the relative 2-5 chords before it.

Since the target chord is a minor, its relative 2nd chord would be ii° or iiø, which is Dø.

So, the secondary 2-5 of Cm is Dø - G7.

Using this in the progression, we get

B♭ - Dø - G7 - Cm - F - Gm

Let's use tritone substitution for G7. We can replace it with D♭7.

The progression becomes:

B♭ - Dø - D♭7 - Cm - F - Gm

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Conclusion

Tritone substitute of a dom7 chord is another dom7 chord that shares the same tritone.

A quick way of finding a tritone sub is to make a dom7 chord on a note that is a tritone away from the root of the chord we want to substitute.

When targeting a particular chord for some temporary tension and resolution, tritone subs can be used. Just play the dom7 chord that is a half step above the target chord.

Tritone subs create a nice chromatic movement, so look out for opportunities where that sound can enhance your progressions.

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Thanks for reading.