The document discusses tritone substitution in music theory, explaining how a dominant chord can be replaced with a minor 7th chord and another dominant chord a flattened 5th above. It emphasizes the importance of the 3rd and 7th notes in creating the chord's qualities and provides examples using the G7 and Db7 chords. The author encourages experimentation with these substitutions to enhance harmonic movement in musical progressions.

1. The tritone substitution
Podcast #2 - Additional notes
© Copyright Darren Dutson Bromley 2012

2. The Tritone Substitution.
Last week we saw it was possible to replace a dominant chord with a minor 7th chord
whose root lies a perfect 5th above. For example the note a perfect 5th above G is D, so it
is possible to substitute Dm7 for G7. This week we’ll take a look at another very common
substitution for a dominant chord often referred to as a tritone substitution.
The term tritone is exactly what it says it is, three tones. A tone on the guitar is the
equivalent to two frets, a semitone which is the smallest recognised interval in western
music is one fret. Starting on the note G, a tone above would give A, a tone above A is B
and a tone above B is C#. This is a tritone.
Often the note a tritone above is referred to by its enharmonic equivalent of b5th rather
than #4th.
It is possible to replace a dominant chord with another dominant chord whose root lies a
flattened 5th above. We could replace a G7 chord with Db7 in a sequence and surprisingly
it doesn’t sound out of place or unusual.
For example.
Could be played as
There are a number of reasons why this works so well. The active ingredients in a G7
chord are the 3rd and the 7th. All chords are built from scale tones, a dominant 7th can be
built using the 1st (root) 3rd, 5th and b7th tones of a major scale.

3. The G major scale consists of the notes
G A B C D E F# G
The root note is G, the third note is B, the fifth note is D and the flattened seventh is F.
These are the notes from which a G7 chord is constructed
G B D F
Looking at the function of each of these notes. The role of the root note is to name the
chord, the 5th adds a bit of padding (unless it is altered), the 3rd is very important as it
dictates the tonality of the chord, whether the chord is major or minor, and the 7th is also
very important as it prescribes function, whether the chord needs to resolve onto another
chord or not.
All the active information of a dominant 7th is contained within the 3rd and the 7th.
Looking at the notes of a Db7 chord, the substitute chord for G7, we have these notes
The Db major scale: Db Eb F Gb Ab Bb C Db
Db7 chord:! Db F Ab Cb
! ! ! root 3rd 5th b7th
The F and the B (Cb), the two active ingredients of a G7 chord are also present giving the
Db7 chord the same qualities as G7.
An easier way to find a note a tritone above is one note higher on the next string. This
works across all the strings apart from the third string due to the second string being tuned
differently, here it is two frets higher.

4. The chords to the classic piece Georgia On My Mind by Hoagy Carmichael look like this.
Looking at the G#7 chord it is possible to apply the substitution discussed last week. The
note a perfect 5th above G# is D#, we could therefore substitute D#m7 for G#7 or use it to
create more harmonic movement in a bar by including both chords.
The note a tritone above G# is D allowing us to substitute the chord D7 for G#7.
We could also include the two substitute chords in the bar.
It is also possible to include the original chord. This creates much more harmonic
movement in the bar and the chords resolve beautifully on to C#m7 by moving
chromatically towards it.
Try using these substitutions in different chord progressions; they are an excellent way of
creating different colours and variations in a sequence.
See you next time