Aeolian harmony
Aeolian harmony [1] is harmony or chord progression created from chords of the Aeolian mode. Commonly known as the "natural minor" scale, it allows for the construction of the following triads (three note chords built from major or minor thirds), in popular music symbols: i, ♭III, iv, v, ♭VI, and ♭VII. The scale also produces iio, which is avoided since it is diminished. The leading-tone and major V which contains it are also not used, as they are not part of the Aeolian mode (natural minor scale). However, Aeolian harmony may be used with mode mixture.
For example, ♭VII, is a major chord built on the seventh scale degree, indicated by capital Roman numerals for seven, respectively.
There are common subsets including i-♭VII-♭VI, i-iv-v and blues minor pentatonic derived chord sequences such as I-♭III-IV, I-IV, ♭VII (The verse of "I'm Your Man"[clarification needed]).[2] All these lack perfect cadences (V-I) and may be thought of as derived from rewrite rules using recursive fourth structures (repeated progression by perfect fourth, see circle progression).[2] Middleton [2] suggests of modal and fourth-oriented structures that, rather than being, "distortions or surface transformations of Schenker's favoured V-I kernel, it is more likely that both are branches of a deeper principle, that of tonic/not-tonic differentiation."