In the previous lesson we learned what the tritone sub is. Now let's begin to look at it's real world applications. A good way to start would be to examine this progression:
As in the previous lesson, we used a generic bebop lick in the first bar and repeated it down a tritone in the second. Those two chords are the germ from which the bridges of countless tunes are built. Let's look at a more conventional treatment of those two chords:
You see a D mixolydian in the first bar and a G mixolydian in the second. Pretty basic stuff. Here's where the tritone sub comes into play. Let's change the G mixolydian to a Db mixolydian (the tritone sub of G). And since the 4th of Db is Gb/F#, which is a no-no over a G7 chord, we'll raise that a half step to G, giving us a Db Lydian Dominant scale:
Play it and see how it sounds. Examine the notes as they relate to the G7 chord. We have the Root, b9, #9, 3, b5, #5 and 7. All the great altered notes. Now what if we extended this chord pattern out to form a full 4 bar bridge and extended the lick? Here's what we get:
There are some heavy dissonances there, but they add a wonderful level of richness to the line. Experiment with this technique further and try it out the next time you play. Good luck!