Take a C major scale. What is the fourth degree or IV of that scale?? F. With me so far? Now what is the 4th interval above F in the C major scale? F, G, A, [u]B[/u], So a fourth above F is B. Okay. What is the name of the interval from F to B. Well a perfect 4th is 2 1/2 steps, and a perfect 5th is 3 1/2 steps. F to B is [u]3 steps[/u], so which is that? A augmented fourth, #4, or TRI-TONE. Right? Now in the C major scale, what is the given name for the fourth degree (F)(IV)? Well it's sub-dominant (sub-tonic if you want to call it that). But anyways a sub-dominant chord is not a dominant chord, nor is it a leading tone chord. Now as you can see the tri-tone exists within the dominant chord, the leading tone chord, and the sub-dominant chord. What was so complicated about that??
If you don't get it, I don't care anymore. Sorry but this is just senseless and pointless. You have your way and I have mine, we'll leave it at that.
"My whole life is a dark room...ONE BIG DARK ROOM" - a.f.i.
