diatónica

Diatónica, in music theory, denotes the diatonic system of Western tonal music. It refers to scales and harmony built from seven pitch classes within an octave, using a standard pattern of whole steps and half steps that defines the major and natural minor scales and their related modes.

The diatonic scale pattern for the major scale is whole, whole, half, whole, whole, whole, half (W-W-H-W-W-W-H). The natural minor scale follows a different but related pattern (W-H-W-W-H-W-W). Other minor scales, such as harmonic and melodic minor, alter certain degrees but remain diatonic within their respective keys. The diatonic collection centers on pitches that belong to a given key, without introducing chromatic alterations outside that key, though borrowed and altered tones may be used for color.

Diatonic harmony is built from triads and seventh chords derived from the diatonic scale degrees. In a major key, the diatonic triads are I, ii, iii, IV, V, vi, and vii°; in a minor key, the corresponding chords are i, ii°, III, iv, v (or V with a raised third), VI, and VII. This system underpins tonal music by defining functional relationships among chords within a key.

Modes associated with the diatonic collection include Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, and Locrian. They use the same seven pitch classes but start on different degrees, giving distinct tonal flavors while remaining diatonic.

Historically, the diatonic system became central in Western music from the Baroque era onward, providing a framework that contrasts with chromaticism and modal practices. In common usage, melodies and harmonies frequently stay within diatonic bounds, with non-diatonic tones employed as color or coloristic borrowings.