The tritone (tri- or three and tone) is a musical interval that spans three whole tones. The tritone is the same as an augmented fourth, which in equal temperament is enharmonic to a diminished fifth. It is often used as the main interval of dissonance in Western harmony, and is important in the study of musical harmony.
Definition and Nomenclature
Only the augmented fourth consists of three whole tones in meantone temperament. This is where the term is derived. Calling the diminished fifth a "tritone" is parlance. Writers often use the term tritone to mean specifically half of an octave from a given tone, without regard to what system of tuning it may belong to. Two tritones add up to six whole tones, which in meantone temperament is a diesis less than an octave, but in equal temperament, where the diesis is tempered out, it is equal to a perfect octave. A common symbol for tritone is TT. It is also sometimes called a tritonus, the name used in German. An equal-tempered tritone m