Chords in Ab Aeolian

Ab Aeolian is built from the notes Ab, Bb, Cb, Db, Eb, Fb and Gb. Its scale carries 7 flats. Harmonising that scale in thirds gives seven chords — 3 majors, 3 minors and 1 diminished — starting on Abm as the i. The chord on the fifth degree is Ebm rather than a major V, so Ab Aeolian has no leading tone and resolves by step and colour instead of by dominant pull — the sound that separates it from a plain Ab major.

Beyond those seven, Ab Aeolian commonly borrows Ab (I), Bbm (ii), Cm (iii), Db (IV) and Eb (V) from the parallel major — the mixture chords that give a progression somewhere unexpected to go.