Notice that the last diminished second is formed by two enharmonically equivalent notes (E в™Ї and F в™®). Using the notes of a chromatic scale, BвЂ“F may be also decomposed into the four adjacent intervalsД«вЂ“C в™Ї (major second), C в™ЇвЂ“D в™Ї (major second), D в™ЇвЂ“E в™Ї (major second), and E в™ЇвЂ“F в™® ( diminished second). For instance, using the notes of the C major scale, the diminished fifth BвЂ“F can be decomposed into the four adjacent intervalsД«вЂ“C ( minor second), CвЂ“D (major second), DвЂ“E (major second), and EвЂ“F (minor second).

To obtain a fifth (for instance, a d5), it is necessary to add another second. The reason is that a whole tone is a major second, and according to a rule explained elsewhere, the composition of three seconds is always a fourth (for instance, an A4). It is not possible to decompose a diminished fifth into three adjacent whole tones. For instance, the interval FвЂ“B is an augmented fourth and can be decomposed into the three adjacent whole tones FвЂ“G, GвЂ“A, and AвЂ“B. In most other tuning systems, they are not equivalent, and neither is exactly equal to half an octave.ДЄny augmented fourth can be decomposed into three whole tones. In twelve-tone equal temperament, the most commonly used tuning system, the A4 is equivalent to a d5, as both have the size of exactly half an octave. They both span six semitones, and they are the inverse of each other, meaning that their sum is exactly equal to one perfect octave (A4 + d5 = P8). The augmented fourth ( A4) and diminished fifth ( d5) are defined as the intervals produced by widening the perfect fourth and narrowing the perfect fifth by one chromatic semitone. Under that convention, a fourth is an interval encompassing four staff positions, while a fifth encompasses five staff positions (see interval number for more details). According to a complex but widely used naming convention, six of them are classified as augmented fourths, and the other six as diminished fifths. Since a chromatic scale is formed by 12 pitches (each a semitone apart from its neighbors), it contains 12 distinct tritones, each starting from a different pitch and spanning six semitones. A musical scale or chord containing tritones is called tritonic one without tritones is atritonic. The condition of having tritones is called tritonia that of having no tritones is atritonia. These various uses exhibit the flexibility, ubiquity, and distinctness of the tritone in music. 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.' The tritone found in the dominant seventh chord can also drive the piece of music towards resolution with its tonic. In classical music, the tritone is a harmonic and melodic dissonance and is important in the study of musical harmony. In twelve-equal temperament, the tritone divides the octave exactly in half as 6 of 12 semitones or 600 of 1200 cents. For instance, the above-mentioned C major scale contains the tritones FвЂ“B (from F to the B above it, also called augmented fourth) and BвЂ“F (from B to the F above it, also called diminished fifth, semidiapente, or semitritonus). According to this definition, a diatonic scale contains two tritones for each octave.

A tritone is also commonly defined as an interval spanning six semitones. For instance, the above-mentioned interval FвЂ“B is the only tritone formed from the notes of the C major scale. According to this definition, within a diatonic scale there is only one tritone for each octave. For instance, the interval from F up to the B above it (in short, FвЂ“B) is a tritone as it can be decomposed into the three adjacent whole tones FвЂ“G, GвЂ“A, and AвЂ“B. In music theory, the tritone is defined as a musical interval composed of three adjacent whole tones (six semitones).

Harmonic and melodic minor scales