ABSTRACT
In jazz, the relationship between chords and scales is explained using chord–scale theory. Chord–scale theory relates certain harmonies to melodies and melodies to harmonies. By extension, chord–scale theory measures the harmonic identity of improvised lines and examines melodies for their harmonic clarity. Finally, chord–scale theory allows to formulate rules of voice leading that govern the behavior of harmonic progressions and melodic lines. A chord built entirely of thirds, so-called tertian formation, has seven notes that can be arranged in the form of a scale. In the forthcoming discussion, modes and chords are placed in the familiar functional categories. The term upper structure refers to a triad or four-part chord that contains extensions or chord tones of an extended harmonic formation. The chord–scale relationship in Lydian illustrates one of many spelling discrepancies that authors will try to untangle. The Dorian mode is an interesting collection with equally interesting chord–scale relationships.
