• Jay EuDaly

The Tritone Substitution (1)

Updated: Sep 7, 2021

“The more you alter a Dominant chord, the more like its Tritone it becomes.”

With that one simple statement, my teacher (John Elliott) explained the Dominant Tritone Substitution; how it works and why it works.

Here’s a technical definition:

  • A Tritone Substitution is the substitution of one Dominant 7th chord (possibly altered or extended) with another (possibly altered or extended) that is three whole-steps (a tritone) from the original chord. It's also known as a Flat-5 Substitution, since a tritone is a flatted 5th (technically speaking, a Diminished 5th) from the original root.

So let’s test John’s maxim, “The more you alter a Dominant chord, the more like its Tritone it becomes.

We’ll start with an open-voiced Bb9:

The Tritone is E. We’ll use a close-voiced E9:

Both of these chords are unaltered. However, if we define the notes of the Bb9 in terms of E, that is, switch the root from Bb to E while leaving everything else the same, the E9 chord is double-altered, namely E7+(b9):

  • Note: the sharped 5th (denoted by the "+" sign), can also be called a, “b13.”

Now we’ll start altering the Bb9, then shift the root to E and see how the Eb7+(b9) has changed. The first thing we’ll do is flat the 9:

So it turns out that flatting the 9th of the Bb naturals the 5th of the E:

Both chords are now single altered; both are Dominant b9.

If we sharp the 5th of the Bb chord we’ve naturaled the b9 of the E:

If we flat the 5th of the Bb (the b5 can also be called a #11), that gives us the root of E, making the E chord an unaltered E7:

So in each case the Bb is now double-altered and the E is unaltered. If I go through every possible alteration of a Bb9 chord the result is always the same; it becomes more like an unaltered E9, E7 or E13. Therefore:

The more you alter a Dominant chord, the more like its Tritone it becomes.

So how does this phenomenon play out in music?

The most obvious application would occur in a Dominant Cycle.


If you don't know what I mean by, "Dominant Cycle," stop right here and download the 5-Lesson Foundational Series. This series of lessons teaches the Circle of Keys as an organizational mechanism by which you ensure that whatever you learn is drilled in every key in all possible positions. It also gives you a method to find any note, anywhere, without memorizing note names on every string. That is a beautiful thing! Since cycles are one of the main ways chords move in music, you really should get a handle on it!

You can download the 5-Lesson Foundational Series right here for free with no further obligation or commitment:



A "Dominant Cycle" is where Dominant 7 chords move in a sequence of 4ths. The Bridge of any Rhythm Changes tune would be an example:

The F7 chord at the end leads to the Bbmaj7 of the last "A" section.

Since each chord lasts 2 bars, we can use the second bar of each chord for the Tritone Substitution:

Keep in mind that even though the chart is written in terms of 7th chords, extensions and alterations can be applied at will, depending on what you want to hear. For example:

Here's one with altered chords:

Tritone Subs in the Blues

Tritone Subs can be used in a 12-Bar Blues context. Here is a typical 12-bar form:

Here's how Tritone Subs can be used to give more movement and interest:

In the next lesson we'll cover the use of Tritone subs in standards that are built on cyclical movement like Autumn Leaves and All the Things You Are, as well as possibilities for a I-VI-II-V Turnaround.


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