AP® Music Theory · Unit 2 · Topic 2.5
The Tritone
A tritone is an interval of six half steps, exactly half of a twelve-half-step octave. It has no stable center, so it sounds restless and pulls strongly toward resolution.
An octave holds twelve half steps. Split it evenly and you get six and six: a tritone on each side. That perfect symmetry is exactly the problem. Every other common interval leans toward a stable-sounding partner, a perfect fifth leans toward its tonic, a major third settles into a triad, but the tritone sits dead center with nothing pulling it one way more than the other. Your ear hears that lack of a home and reads it as tension, so the tritone demands to move somewhere.
Every major scale hides exactly one tritone, built between scale degree 4 and scale degree 7. In G major, that is C up to F sharp. Spelled as an augmented fourth, C to F sharp, the two notes want to spread apart, C sliding down to B and F sharp climbing up to G, landing on a G major third outward. Spelled as a diminished fifth, the same pitches moving the other direction squeeze inward toward each other, resolving into a third just as naturally. Both directions feel right because the interval itself has no preferred center.
This is exactly why a dominant seventh chord resolves so forcefully. Build one on G: G, B, D, F. The third, B, and the seventh, F, form a tritone, and each of those notes sits only a half step from a tonic chord tone, B leaning up to C, F leaning down to E. That half-step proximity plus the tritone's built-in restlessness is what makes V7 snap to I with so much authority, and it is the same engine behind how minor scales and key signatures organize tension within a key.
Key terms
- Tritone
- An interval spanning six half steps, exactly half of a twelve-half-step octave.
- Augmented fourth
- A tritone spelled as a fourth, such as C to F sharp, that typically resolves outward.
- Diminished fifth
- A tritone spelled as a fifth, such as F sharp to C, that typically resolves inward.
- Dominant seventh chord
- A four-note chord built on scale degree 5 containing a tritone between its third and seventh.
Watch it explained
- How it worksHow do three whole steps split an octave into two equal halves?
- How it worksWalk me through where the tritone hides inside an ordinary major scale.
- Worked exampleFind the tritone in G major and show it resolving outward and then inward.
- Ties togetherHow does the tritone inside a dominant seventh chord force that chord toward tonic?
Check yourself
End of topic.