Aeolian & Locrian — the dark side

Aeolian — the natural minor

You already know this one. Aeolian = natural minor.

• Formula: 1 2 ♭3 4 5 ♭6 ♭7
• Compared to major: ♭3, ♭6, ♭7 (three flats).
• Where you hear it: every “sad” rock song ever, “Stairway to Heaven”, “Losing My Religion”, almost every minor-key pop song.

Aeolian is essentially the default minor mode. When someone says “play in A minor”, they usually mean Aeolian (which is the relative minor of C major).

Locrian — the wild card

• Formula: 1 ♭2 ♭3 4 ♭5 ♭6 ♭7
• Compared to natural minor: same, but with both a ♭2 and a ♭5.
• Mood: deeply unstable. The tonic chord of Locrian is a diminished triad (1, ♭3, ♭5), which contains a tritone — and so Locrian can’t really rest on its own tonic.
• Where you hear it: rarely as a song’s main mode. Used in metal, jazz fusion, and as a passing mode over diminished or m7♭5 chords.

When you actually use Locrian

Locrian’s natural home is the vii° chord in a major key. In C major, that’s B diminished (B D F). When a song briefly visits this chord, Locrian is the matching scale.

It’s also used in jazz over m7♭5 (half-diminished) chords, which are common in minor ii-V-i progressions: “Dm7♭5 - G7♭9 - Cm”.

Outside of those technical uses, Locrian is more of a colour to dip into than a home to live in.

A summary of modes by brightness

A mental map from brightest to darkest:

Lydian → Ionian → Mixolydian → Dorian → Aeolian → Phrygian → Locrian

Each step down lowers one note by a half-step compared to the previous:

• Lydian: 1 2 3 ♯4 5 6 7
• Ionian: 1 2 3 4 5 6 7 (lower the 4)
• Mixolydian: 1 2 3 4 5 6 ♭7 (lower the 7)
• Dorian: 1 2 ♭3 4 5 6 ♭7 (lower the 3)
• Aeolian: 1 2 ♭3 4 5 ♭6 ♭7 (lower the 6)
• Phrygian: 1 ♭2 ♭3 4 5 ♭6 ♭7 (lower the 2)
• Locrian: 1 ♭2 ♭3 4 ♭5 ♭6 ♭7 (lower the 5)

This is one of the most useful mental models in modal music. It tells you exactly what makes each mode different from its neighbour.

Try this

Pick a single root note — say E. Play all seven modes starting from E one after another:

1. E Lydian: E F♯ G♯ A♯ B C♯ D♯
2. E Ionian (major): E F♯ G♯ A B C♯ D♯
3. E Mixolydian: E F♯ G♯ A B C♯ D
4. E Dorian: E F♯ G A B C♯ D
5. E Aeolian (natural minor): E F♯ G A B C D
6. E Phrygian: E F G A B C D
7. E Locrian: E F G A B♭ C D

Listen as each mode darkens by exactly one note. This is the parallel-mode view, and it’s how jazz musicians actually think about modes.