Tritones are in Dominant 7th, 9th, 11th chords as well as diminished and half-diminished chords.
to build on this theory, tritones are used most commonly, to substitute for a dominant/diminished chord. So for the poster who was asking which tritone do you use with each scale degree, I say, which dominant chord are you trying to substitute? Any 5 chord in major progression, but especially in minor progressions, you can use it. Minor progressions have some extra tensions already built into the dominant chord, which makes for an easier and much more appropriate sounding tritone sub.
So, simply whenever you're ready to substitute outa dominant/diminsihed chord and replace it with a tritione chord, do this
#1) play the 3rd and 7th (dominant) degree in your left hand. most people play it with their 2nd and pinky finger
#2) play a triad 1 whole step below the dominant 7th degree in your left hand.
Voila, tritone!
ex.
minor 2-5
CG/BbEbGb
FC/AC#EbG#
BbF/AbBbDbF
with tritone instead
minor 2-5 (tritone sub)
CG/BbEbGb
AEb/AbDbF
BbF/AbCDbF
Yeah its a lot to think about, but after a while you get the hang of it, and you can try different mutations of the above directions to get more interesting results. When I first started tritones, as I would get close to that part in the song, i kept visually picturing the 5 chord in my head, that I wanted to substitute. Sometimes, Id miss it on thhe first go round, but I thought about the 5, then, think about the 3rd and 7th of that 5 chord, then, think of the what note is one wholestep down from the top note in my LH tritone, and play its triad. Its really simple, but must be practiced.
notice how close the right hand chords are to each other, thats why I just changed the voicing in my 1 chord just a lil for variety.
