intervallid

Intervallid are distances between two pitches and describe how far apart two notes lie in pitch. In music theory they underpin both harmony and melody. Intervals can be described by their size (the number of letter names spanned) and their quality (diminished, minor, major, perfect, augmented). They are harmonic when the two notes sound together, and melodic when they are played in sequence.

In Western tuning, intervals are named by their diatonic size: second, third, fourth, fifth, sixth, seventh, and octave (the unison is often treated as the starting point). Among these, unison, fourth, fifth, and octave are called perfect intervals; others can be major or minor and may be altered to diminished or augmented forms. The most common quality pairings are major/minor and perfect. For example, the interval from C to E is a major third, from C to F is a perfect fourth, from C to G is a perfect fifth, and from C to Ab is a minor sixth. Intervals are also measured in semitones within an octave: 0 through 12, corresponding to unison up to an octave.

Inversions reverse the order of the two notes. Inversions change quality: a major becomes a minor and a minor becomes a major; augmented becomes diminished and vice versa; perfect intervals remain perfect. Intervallid are essential in constructing chords, analyzing melodies, and understanding tonal relationships; they are foundational in tuning systems and transposition.