An interval of six semitones — an augmented 4th or diminished 5th. It exactly splits the octave in half, which is why it's the only interval that's its own inversion.

Music Theory · Chapter 5, Lesson 7 — Intervals

The Tritone

Q: Why is the tritone called the devil's interval?

Medieval theorists called it 'diabolus in musica' (the devil in music) because its harsh dissonance was considered unstable and difficult to sing in tune, and it was often avoided in early church music.

Q: Is the tritone always bad-sounding?

No — while tense on its own, it's used purposefully throughout blues, jazz, metal, and classical music. It's a key ingredient of the dominant 7th chord, where its tension drives the resolution to the tonic.

Q: How does the tritone relate to dominant 7 chords?

A dominant 7th chord's 3rd and 7th form a tritone. In a V7-to-I cadence, that tritone resolves outward or inward by a semitone into the major 3rd of the tonic chord, which is what gives the cadence its strong pull to resolve.

Six semitones, exactly half an octave, and centuries of nicknames like "the devil's interval" — the tritone is music's most famous source of tension.

Intermediate ⏱ 5 min read 🎹 Interactive

What is a tritone?

A tritone is an interval of six semitones — depending on spelling, an augmented 4th or a diminished 5th. It's exactly half of an octave (12 semitones), which makes it the only interval that's identical to its own inversion: flip a tritone upside down and you get another tritone.

The devil's interval

Medieval music theorists nicknamed the tritone "diabolus in musica" — the devil in music. Its harsh, unresolved dissonance was considered so unstable that it was often avoided outright in early church music. The nickname stuck, and composers ever since have used the tritone deliberately whenever they want tension, unease, or drama.

🎹 Tritone Explorer Pick a root, hear the tritone, then hear it resolve like a V7 chord into its tonic.

Root

Root note Tritone above 6 semitones apart — exactly half an octave.

The tritone in dominant 7 chords

Every dominant 7th chord contains a tritone between its 3rd and 7th. In a classic V7→I cadence, that tritone resolves by stepping a semitone inward or outward into the major 3rd of the tonic chord — that motion is exactly what gives the cadence its powerful pull toward resolution. It's why the "Hear it resolve" button above lands so satisfyingly.

💡 Trivia: The opening two notes of Black Sabbath's song "Black Sabbath" are a tritone — a deliberate nod to its "devil's interval" reputation, and a major influence on the sound of heavy metal.

Common questions

What is a tritone?

An interval of six semitones — an augmented 4th or diminished 5th. It splits the octave exactly in half, making it its own inversion.

Why is the tritone called the devil's interval?

Medieval theorists called it "diabolus in musica" because its harsh dissonance was considered unstable and hard to sing in tune, and it was often avoided in early church music.

Is the tritone always bad-sounding?

No — it's used purposefully across blues, jazz, metal, and classical music, and is a key ingredient of the dominant 7th chord.

How does the tritone relate to dominant 7 chords?

A dominant 7th's 3rd and 7th form a tritone. In a V7-to-I cadence, it resolves by a semitone into the tonic chord's major 3rd, driving the resolution.

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What is a tritone?

The devil's interval

The tritone in dominant 7 chords

Common questions

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