In music theory, the tritone is defined as a musical interval composed of three adjacent whole tones (six semitones).[1] For instance, the interval from F up 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. According to this definition, within a diatonic scale there is only one tritone for each octave. For instance, the above-mentioned interval F–B is the only tritone formed from the notes of the C major scale. A tritone is also commonly defined as an interval spanning six semitones. According to this definition, a diatonic scale contains two tritones for each octave. For instance, the above-mentioned C major scale contains the tritones F–B (from F to the B above it, also called augmented fourth) and B–F (from B to the F above it, also called diminished fifth, semidiapente, or semitritonus).[2] In twelve-equal temperament, the tritone divides the octave exactly in half as 6 of 12 semitones or 600 of 1200 cents.[3]

Other namesaugmented fourth, diminished fifth
AbbreviationTT, A4, d5
Interval class6
Just intervalPythagorean: 729:512, 1024:729
5-limit: 25:18, 36:25; 45:32, 64:45
7-limit: 7:5, 10:7
13-limit: 13:9, 18:13
Equal temperament600
Just intonationPythagorean: 612, 588
5-limit: 569, 631; 590, 610
7-limit: 583, 617
13-limit: 563, 637

In classical music, the tritone is a harmonic and melodic dissonance and is important in the study of musical harmony. The tritone can be used to avoid traditional tonality: "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."[4] The tritone found in the dominant seventh chord can also drive the piece of music towards resolution with its tonic. These various uses exhibit the flexibility, ubiquity, and distinctness of the tritone in music.

The condition of having tritones is called tritonia; that of having no tritones is atritonia. A musical scale or chord containing tritones is called tritonic; one without tritones is atritonic.