What is interval?

The distance between two pitches, named by how many letter-names it spans and its quality — a major third, a perfect fifth. Intervals are the raw material of both melodies and chords.

An interval measures the gap between two notes. Its size is the number of letter-names it covers (C up to E is a third; C up to G is a fifth), and its quality — major, minor, perfect, augmented, diminished — fine-tunes that size by a . The same two-note gap sounds the same wherever you play it, which is why musicians think in intervals rather than absolute notes: stack them and you get chords, string them in a line and you get melody.