Intervals

What this section teaches

An interval is the distance between two notes, measured in half steps — and it is the single most load-bearing idea in music theory. Melodies are sequences of intervals; chords are stacks of them; scales are patterns of them; and what your ear calls "sweet," "sad," or "tense" is mostly interval quality. There are thirteen simple intervals, from the unison (zero half steps) to the octave (twelve), and each has a stable character that survives any change of key, register, or instrument. That is why interval training transfers everywhere: learn what a minor third sounds like once, and you will recognize it for life.

How to use these pages

Each interval's page gives its size in half steps and cents, its just-intonation frequency ratio (the physics of why some intervals ring smoothly), its inversion, well-known melodies that open with it — the classic way to anchor an interval in your ear — and the chords that contain it. Start with the thirds and the perfect fifth: those three distances alone explain major, minor, and most of what chords do.

Where to go next

Hear how intervals stack into chords, chain into scales, and give the tritone its starring role in tension and resolution. To name the distance between any two notes instantly, use the interval calculator.