Interval

Full Description

An interval is the distance in pitch between two notes, measured in degrees of the scale. It is one of the most important concepts in music theory, underpinning melody, harmony, chord construction, and counterpoint. Every chord is built from intervals; every melodic step is an interval. Intervals are named by the number of scale degrees they span. A second spans two notes (C to D), a third spans three (C to E), a fourth spans four (C to F), and so on up to an octave (C to C, spanning eight degrees). Beyond the octave, intervals are called compound — a ninth is an octave plus a second, a tenth an octave plus a third. The quality of an interval — major, minor, perfect, augmented, or diminished — refines this measurement. Perfect intervals (unison, fourth, fifth, octave) have a hollow, stable sound. Major and minor intervals differ by a semitone; a major third (C to E) has a bright, open quality, while a minor third (C to E flat) sounds softer and more ambiguous. Augmented intervals are a semitone wider than perfect or major; diminished intervals a semitone narrower than perfect or minor. Harmonic intervals occur when two notes sound simultaneously; melodic intervals occur consecutively. Ear training — the ability to identify and sing intervals by ear — is a core skill in music education. Recognising a perfect fifth or a minor sixth without conscious thought is the foundation of musical literacy.