just playing the root and tritone together is hard to use musically because it's dissonant. Here's a more musical example from a song you should know.
Code:
Black Sabbath "Black Sabbath"
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----5---tr---------5-----------
-5-----4(5)----5------4~------
-3-------------3---------------
the 4 is the tritone, or augmented 4th or diminished 5th from the G5 power chord. its like.. semantics and shit. but either way you can hear how dark it sounds. http://en.wikipedia.org/wiki/Tritone
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