Originally posted by griphon2
As for IV chords. I prefer to look at them as sub-tonics, rather than subdominant. It's just a preference. Once you add or imply a tritone, it's dominant.

I'm just stating from what you wrote man. Since I think we're talking about chord names, like V is dominant and IV is subdominant. A tri-tone does exist within the IV chord, it's the #4. A tri-tone is just the name of the interval that is 3 steps, whether it's #4 or b5. It's still a tri-tone. That's all I'm trying to say. Oh the fact that the tri-tone is always dominant, I can't agree but if it's your way to look at it. Cool. I wouldn't neglect the fact that the tri-tone exists in diminished chords though. Especially if your looking in terms of function. The tri-tone would also exist in any b9 chord, m6, and many others.