In Part 1 of our article on tritone substitutions we discussed the tritone interval, the tritone substitution, and the theory behind why tritone substitution works. Here in Part 2 of our discussion on tritone substitution we will go through some specific examples of how tritone substitution works in practice and discuss some ideas for improvisation. Let's get started!
As we learned in Part 1, tritone substitution is the act of replacing one dominant 7th chord with another dominant 7th chord a tritone away. We can use tritone substitution anytime we encounter dominant 7th chords. But just because we can do something, does not mean that we always should do something. The tritone sub is a very distinct sound, characteristic of jazz and Broadway-style tunes. You should definitely practice with this device and get accustomed to its sound as much as possible, but this general rule of thumb is good advice: everything in moderation.
Let's look at real-music instances in which you might choose to utilize tritone subs. We'll start with the first few measures of the jazz standard, "My Romance."
As we look at the first few measures of "My Romance," we notice that there are only two dominant 7th chords - the F7 and D7. These are the only two chords for which we can use a tritone substitution. Let's see how we might arrange that for solo piano, both with the original chords...
...and the tritone subs [F7 = B7 and D7 = Ab7]:
Remember that you don't have to use either of these tritone subs, or you can use them both, or you can use just one and not the other. Practice, experiment, and decide which you like best. Also, listen to other players, transcribe, and check out our lessons which go into detail discussing various ways to use tritone subs.
Tritone substitutions can be very helpful in an improvisational context as well. Consider the first 8 bars of a 12-bar blues in the key of C:
Notice that most of the chords above are dominant 7th chords. This means that we could use a tritone sub for any of those dominant 7th chords, but doing so would really change the sound of this C blues. But let's look at measure 4 because this is a great example of where advanced players often use a tritone sub. The original chord in measure 4 is a C7 chord. If we use a tritone sub, the resulting chord would be a Gb7 chord. To create some real contrast, advanced players might solo over C7 in measure 3 but then treat measure 4 as a Gb7 chord, choosing to use a scale such as Gb lydian dominant.
The beauty of this is that it really doesn't matter whether the bass player (if there is one) plays a C or Gb in this measure. Since tritone subs are related to the original dominant chord, a bass player can play a 'C' while a pianist might play a Gb7 chord and solo using a Gb lydian dominant scale.