A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.
The tritone (augmented fourth or diminished fifth, 6 semitones) is the most dissonant interval and historically called 'diabolus in musica'—it has a uniquely unstable quality. Augmented intervals sound wide and pull outward; diminished intervals sound narrow and pull inward. Learning to recognize these by ear is essential for harmonic analysis, voice leading, and understanding the tritone's role in dominant seventh and other functional chords.
Hear tritones in context within dominant seventh chords (the tritone between the third and seventh), then practice augmented and diminished intervals in isolation. Compare the tritone's instability with the stability of perfect and major/minor intervals.
Dismissing augmented and diminished intervals as uncommon or unimportant. Failing to hear the tritone within seventh chords because it's embedded in the chord's color rather than presented as an isolated melodic interval.
You've studied interval quality — you know that intervals are classified by their size in half-steps and their quality (perfect, major, minor, augmented, diminished). Now the task is to hear these qualities directly, and among all the intervals, the tritone (augmented fourth / diminished fifth, spanning exactly 6 semitones) is the most important to recognize because of its distinctive, immediately perceptible instability. Medieval theorists called it *diabolus in musica* — the devil in music — not because it sounds evil, but because it resists rest in a way that no other interval does.
The best way to understand the tritone's character is through contrast. Recall that a perfect fifth (7 semitones) sounds completely stable — it's the most consonant interval after the unison and octave, with an almost hollow resonance. A perfect fourth (5 semitones) shares that stability in melodic contexts. The tritone sits exactly between these two — neither a fourth nor a fifth, but split evenly. That ambiguity is what makes it unstable: the ear hears two pitches that don't quite belong together, that seem to pull in different directions. Play C and F# together and you'll feel the interval's restlessness immediately.
Augmented intervals sound wide — wider than expected, with a pulling-outward quality. Diminished intervals sound narrow — compressed, with a pulling-inward quality. The tritone is both simultaneously: as an augmented fourth, it sounds wider than a perfect fourth; as a diminished fifth, it sounds narrower than a perfect fifth. This ambiguity is what makes the tritone harmonically flexible — it can resolve either by expanding to a sixth (augmented fourth resolving out) or by contracting to a third (diminished fifth resolving in). Which resolution occurs depends on the harmonic context, which is why the tritone is the engine of dominant seventh chord function: in a G7 chord, the tritone between B (the third) and F (the seventh) resolves with B moving up to C and F moving down to E, spelling out the C major arrival.
To train your ear to hear tritones and other dissonant intervals, start with the dominant seventh chord as context rather than isolated intervals. The tritone *within* a V7 chord is embedded — you hear it as chord color, as tension, as the urgent need to resolve. Then practice isolating it melodically: sing up a major third and a minor second to reach the tritone, or down a minor second from a perfect fifth. Reference melodies can help anchor the sound in memory — the opening of "The Simpsons" theme outlines a tritone, as does the bridge of "Maria" from West Side Story ("Ma-ri-a! I just met a girl named Maria"). Augmented and diminished seconds, fourths, and fifths appear frequently in chromatic contexts, and recognizing their telltale quality — that sense of tension needing resolution — is what allows you to track harmonic function by ear rather than just by note-counting.
Topics in reflective domains aren't scored by quiz answers. Read, reflect, and mark when you've thought it through.