In music theory, the “natural minor” scale has a flat 7th. A whole tone between the 7th note of the scale and the tonic. So a triad on the dominant will make a minor chord. For example, in A minor, natural (all the white keys on the piano from A to A’), there will be an e minor chord as the dominant, because the G natural is a minor third up from E.
But Western harmony since the Renaissance has used a raised 7th in minor scales, so that the dominant triad in A minor will come out E major, with the 7th note G bumped up to G#. The explanation for why it’s preferred that way is to have the strong feeling of the leading tone pulling you home to the tonic, the place of repose. With only a half tone between the raised 7th and the tonic, you get that strong pulling feeling like you’re almost there. Like a rock climber reaching the edge of a cliff and her buddy is there to grab her hand and pull her all the way up where she can rest. The whole tone interval between the flat 7th and the tonic lacks that feeling of tension or pull. It just sort of seems to sit there.
My question is where did this “harmonic minor” raised-7th tweak come from? There was no such thing known in the ancient Greek modes or in the medieval church modes, in Gregorian chant, or most European folk music. The old modes didn’t reappear in Western popular music until the 1950s, under the influence of folk music and blues (and 20th century classical composers like Béla Bartók had been reintroducing the modes under the influence of peasant folk music). In all of the minor modes (Aeolian, Dorian, Phrygian), there was no sharp 7th. Somehow around the time of the Renaissance, or shortly thereafter, Western art music was narrowed down to only two modes: the Ionian (major) and the Aeolian (natural minor)—but then that got tweaked to have a harmonic minor, to have a dominant major resolving into a tonic minor. How did this idea get started?
