The harmonic minor arises from the natural (Aeolian) minor by raising the seventh degree. This change restores to the mode a sharp leading tone, needed for a strong, convincing resolution of the dominant to the tonic — which is precisely why the scale is called “harmonic.”
Between the raised seventh and the low sixth degree an unusual, wide step appears — the augmented second, which gives the harmonic minor its recognizable “Eastern,” exotic colour. This scale underlies most classical minor works and at the same time sounds in the folk music of the Middle East, the Balkans, and the Jewish tradition. The harmonic minor is a kind of compromise between modal archaism and the demands of classical functional harmony.
