Tritone (Augmented 4th)

General info

Name

Tritone (Augmented 4th)

Quality

Tritone

Degree distance

3 whole tones (exactly half an octave)

Semitones

6

Short description

Six semitones — exactly in the middle of the octave. One of the most tense intervals, with a strong pull toward resolution.

Interval structure

Lower note

Root

Upper note

Tritone (#4 / b5)

Degree formula

II6 stIV# / VbIV# / Vb

Semitone formula

6 semitones (3 whole tones)

Interval construction

Interval formula

TT (A4 / d5)

How it's built

From the root, move up exactly six semitones — precisely to the middle of the octave.

Brief explanation

The tritone is the most unstable interval, dividing the octave exactly in half. Historically called the "devil's interval" (diabolus in musica). Can be interpreted as an augmented 4th (#4) or diminished 5th (b5).

How the interval sounds

Sound character

The tritone sounds maximally tense, anxious, and "ominous." It creates the strongest sense of instability and incompleteness. In medieval times, it was forbidden in church music. Today, the tritone is a key element of blues, jazz, rock, and film music. It is the tritone that creates the "devilish" rock feel in Black Sabbath.

Consonance / dissonance

Explanation

The tritone is a strong dissonance. Six semitones divide the octave exactly in half, creating the most unstable frequency ratio. The tritone is the only interval that inverts to itself (a tritone inverts to a tritone).

Tendencies & resolutions

Behavior

The tritone is the most unstable interval, with the strongest tendency to resolve. It can resolve "outward" — by contrary motion to a 6th (minor or major). Or "inward" — by converging to a 3rd. In a dominant 7th chord (G7 in C), the tritone B–F resolves: B → C, F → E.

Harmonic context

Context

The tritone is the key interval of the dominant 7th chord (between degrees III and VII of the major scale). It is the tritone that creates the dominant's "pull" to the tonic. It appears in 7, dim, dim7, and m7b5 chords. In the blues scale, the tritone is the characteristic "blue note." In jazz, tritone substitution is an important harmonic device.

Interval inversion

Interval from every note