The Aeolian mode is a musical mode or, in modern usage, a diatonic scale also called the natural minor scale. On the white piano keys, it is the scale that starts with A. Its ascending interval form consists of a key note, whole step, half step, whole step, whole step, half step, whole step, whole step. That means that, in A aeolian, you would play A, move up a whole step to B, move up a half step to C, then up a whole step to D, a whole step to E, a half step to F, a whole step to G, and a final whole step to a high A.
History
The word Aeolian, like the names for the other ancient Greektonoi and harmoniai, is an ethnic designation: in this case, for the inhabitants of Aeolis —the Aeolian Islands and adjacent coastal district of Asia Minor. In the musictheory ofancient Greece, it was an alternative name for what Aristoxenus called the Low Lydian tonos, nine semitones higher than the lowest "position of the voice", which was called Hypodorian. In the mid-16th century, this name was given by Heinrich Glarean to his newly defined ninth mode, with the diatonicoctave species of the natural notes extending one octave from A to A—corresponding to the modern natural minor scale. Up until this time, chant theory recognized eight musical modes: the relative natural scales in D, E, F and G, each with their authentic and plagal counterparts, and with the option of B instead of B in several modes. In 1547, Heinrich Petri published Heinrich Glarean's Dodecachordon in Basel. His premise had as its central idea the existence of twelve diatonic modes rather than eight, including a separate pair of modes each on the finals A and C. Finals on these notes, as well as on B, had been recognized in chant theory at least since Hucbald in the early tenth century, but they were regarded as merely transpositions from the regular finals a fifth lower. In the eleventh century, Guido d'Arezzo, in chapter 8 of his Micrologus, designated these transposed finals A, B, and C as "affinals", and later still the term "confinal" was used in the same way. In 1525, Pietro Aaron was the first theorist to explain polyphonic modal usage in terms of the eightfold system, including these transpositions. As late as 1581, Illuminato Aiguino da Brescia published the most elaborate theory defending the eightfold system for polyphonic music against Glarean's innovations, in which he regarded the traditional plainchant modes 1 and 2 at the affinal position as a composite of species from two modes, which he described as "mixed modes". Glarean added Aeolian as the name of the new ninth mode: the relative natural mode in A with the perfect fifth as its dominant, reciting tone, reciting note, or tenor. The tenth mode, the plagal version of the Aeolian mode, Glarean called Hypoaeolian, based on the same relative scale, but with the minor third as its tenor, and having a melodic range from a perfect fourth below the tonic to a perfect fifth above it. Although scholars for the past three centuries have regarded the modes added by Glarean as the basis of the minor/major division of classical European music, as homophonic music replaced Renaissance polyphony, this is an oversimplification. Even the key of A minor is as closely related to the old transposed modes 1 and 2 with finals on A—as well as to mode 3 —as it is to Glarean's Aeolian. In modern usage, the Aeolian mode is the sixth mode of the major scale and has the following formula: The Aeolian mode is the sixth mode of the major scale, that is, it is formed by starting on the sixth degree of the major scale. For example, if the Aeolian mode is used in its all-white-note pitch based on A, this would be an A-minor triad, which would be the submediant in the relative major key of C major.
Aeolian harmony 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, in popular music symbols: i, III, iv, v, VI, and VII. The scale also produces ii, 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. 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. 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. All these lack perfect cadences and may be thought of as derived from rewrite rules using recursive fourth structures. Middleton 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."
