Aeolian mode, or minor mode, is one of the most commonly used modes (the other being Ionian mode) in tonal music, featuring a darker sound due to its lowered mediant. The minor mode is more flexible than the major mode as the submediant and the leading tone are variable, creating variants of minor scales:
- To build a natural minor scale (aeolian mode): W-H-W-W-H-W-W
- To build a harmonic minor scale, take the natural minor scale and raise the the last scale degree (the subtonic in natural minor scales) by a half step (in both the ascending & descending line). This is to create a leading tone that evokes a sense of musical closure.
- To build a melodic minor scale, take the natural minor scale and raise the seventh scale degree by a half step in the ascending line only. The reason for keeping the subtonic in the descending line is to preserve the smooth stepwise motion that leads toward the dominant.
Note that these three variations are more like a nine-pitch-class repository of notes to draw from (e.g. for building melodies / harmonies) than actual, distinct scales.