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Introducing Tri-tone Substitution by Tom Quayle

Hi guys and welcome to my column for this issue. Previously, we’ve been expanding our harmonic palette by studying the hugely important II-V-I progression, starting with the basic form before moving onto expanding the progression through a major key with secondary II-V-I movements. In this issue we’ll be learning another cool technique for expanding our palette even further. This technique is known as ‘ Tri-Tone Substitution ’ and sounds a lot more complex than it actually is.

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Before we continue, let me just re-iterate that nothing in music is like rocket science even though, at times, we may use fairly complex names for some of the concepts. Tri-tone substitution is no exception to this so don’t be afraid of the name, just take a deep breath and all will be revealed.

A tri-tone interval is exactly what it says – the musical distance of three tones. You can find a tri-tone interval on your guitar in a couple of ways. The first is to count up three tones from your starting note and since a tone is two frets this will give you a distance of six frets. The other, and more useful way, is to find your root note and simply go up a fret and up a string giving you something that looks like a flattened power chord (also known as a b5 interval).

Tri-tone substitution refers to the idea that we can take an existing V chord (a dominant 7 th chord) and substitute another dominant 7 th chord in its place up a tri-tone. Let’s look at an example and then I’ll explain why this works. In our basic II- V-I in C major (Dm7 – G7 – Cmaj7) we get a G7 for the V chord. If we go up a tri-tone from G we get the note C# or Db and can use a dominant 7 th chord from this new note instead of the original G7. This would give us the progression Dm7 – Db7 – Cmaj7. Notice how the root movement is now going down in semitones giving a smoother sound to the progression.

The reason this works is due to the construction of dominant 7 th chords. Our G7 chord contains a tri-tone interval already thanks to its F and B notes – the 7 th and 3 rd respectively. The Db7 chord also contains these two notes but they are now the 3 rd and 7 th of the chord instead. Only the root note has changed and it is this common tri-tone interval that glues the two chords together meaning that they can be exchanged with one another freely.

The tri-tone interval within both chords acts as a leading tension that resolves when followed by the Cmaj7 chord. Try it for yourself, playing each V chord starting with the G7 and then repeat the progression with the Db7 instead.

You’ll hear that both chords lead very successfully to the Cmaj7 I chord. In the video example I use a Db9 chord to add a bit of colour to the chord but you can use almost any dominant 7 th chord type as long as it includes the notes B and F leading into the Cmaj7 chord. Simply use your ears as a guide.

The technique can also be with minor II-V-I progressions in exactly the same way to produce a tri-tone substituted minor II-V-I. I’ve written some examples out for you in the Tablature so you check these sounds out immediately.

We’ll deal with how to solo over these kind of progressions at a later stage, where you’ll need to develop a more intimate knowledge of dominant 7 th chords and their related scales, but for now try using tri-tone substitutions in your playing and practice slowly to make it a solid part of your repertoire.

See you next time for more harmonic madness!

Good luck,

Tom

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