Chords in A Aeolian

A Aeolian is built from the notes A, B, C, D, E, F and G. It uses no sharps or flats at all. Harmonising that scale in thirds gives seven chords — 3 majors, 3 minors and 1 diminished — starting on Am as the i. The chord on the fifth degree is Em rather than a major V, so A Aeolian has no leading tone and resolves by step and colour instead of by dominant pull — the sound that separates it from a plain A major.

Beyond those seven, A Aeolian commonly borrows A (I), Bm (ii), C#m (iii), D (IV) and E (V) from the parallel major — the mixture chords that give a progression somewhere unexpected to go.