Tritone

In music theory, a tritone is a musical interval spanning three whole tones. For instance, the interval from F to the B above it (in short, F–B) is a tritone as it can be decomposed into the three adjacent whole tones F–G, G–A, and A–B.

In 12-tone-equal temperament, the tritone divides the octave (which is 12 semitones or 1200 cents) exactly in half, making it six semitones, or 600 cents.

In traditional functional harmony, the tritone is a harmonic and melodic dissonance and tritones in chords push toward resolution. For instance, the tritone(s) found in diminished triads as well as the dominant, half-diminished, and fully diminished seventh chords push toward resolution to the tonic. On the other hand, the tritone can also be used to avoid tonality altogether, as composer Reginald Smith Brindle explains: "Any tendency for a tonality to emerge may be avoided by introducing a note three whole tones distant from the key note of that tonality."