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<h1>Locrian Mode</h1>
<p>Locrian is the seventh mode of the major scale and the most theoretically problematic one. It has a diminished 5th above the root — which means there's no stable perfect fifth to anchor the tonic chord. The tonic chord built from Locrian is a half-diminished chord (m7♭5), which by nature sounds unresolved. Locrian is hard to use melodically as a tonal centre because it refuses to feel like home. That instability is its only usable quality — and it's used exactly for that.</p>

<h2>Construction</h2>
<pre>
The seventh mode of the major scale — starts on the 7th degree.
B Locrian = C major scale starting on B:
B C D E F G A B

Formula:      1  ♭2  ♭3  4  ♭5  ♭6  ♭7
Step pattern: H  W   W   H  W   W   W

Compare to Phrygian: 1 ♭2 ♭3 4 5 ♭6 ♭7 (same, but with natural 5th)
Locrian takes Phrygian and also lowers the 5th — maximum flatness.
</pre>

<h2>Locrian in Common Keys</h2>

<table>
  <thead><tr><th>Locrian root</th><th>Notes</th><th>Parent major key</th><th>The ♭5</th></tr></thead>
  <tbody>
    <tr><td>B Locrian</td><td>B C D E F G A</td><td>C major</td><td>F</td></tr>
    <tr><td>E Locrian</td><td>E F G A B♭ C D</td><td>F major</td><td>B♭</td></tr>
    <tr><td>A Locrian</td><td>A B♭ C D E♭ F G</td><td>B♭ major</td><td>E♭</td></tr>
    <tr><td>D Locrian</td><td>D E♭ F G A♭ B♭ C</td><td>E♭ major</td><td>A♭</td></tr>
    <tr><td>F# Locrian</td><td>F# G A B C D E</td><td>G major</td><td>C</td></tr>
    <tr><td>C# Locrian</td><td>C# D E F# G A B</td><td>D major</td><td>G</td></tr>
  </tbody>
</table>

<h2>Sound and Character</h2>
<p>Dark, unstable, and tense — uniquely so because the ♭5 removes the most stable interval (perfect 5th) from the tonic chord. The im7♭5 chord built on the Locrian root sounds half-diminished by nature: it already wants to resolve. Extended Locrian creates a sense of persistent unresolved tension — not building to a climax, just hovering in an uncomfortable space. This makes it useful for horror, avant-garde, and extreme metal contexts where sustained harmonic instability is the goal.</p>

<h2>The Tonic Chord Problem</h2>
<pre>
B Locrian tonic chord: B D F A = Bm7♭5 (half-diminished)
  B to D = minor 3rd ✓
  B to F = diminished 5th (tritone) ← the problem — not stable
  B to A = minor 7th ✓

The diminished 5th (B→F) makes the chord sound unresolved by definition.
There's no perfect 5th anchor — nowhere to land.

Compare:
  Bm7 (Dorian): B D F# A — the F# makes it stable
  Bm7♭5 (Locrian): B D F A — the F makes it inherently unstable
</pre>

<h2>Practical Use: Over Half-Diminished Chords</h2>
<p>The main practical application of Locrian is over m7♭5 (half-diminished) chords in jazz — specifically the ii° chord in a minor ii°-V7-i progression:</p>
<pre>
Minor ii-V-i in A minor:
  Bm7♭5 → E7 → Am

Over Bm7♭5: B Locrian
  Chord tones: B (root), D (♭3), F (♭5), A (♭7) — all in B Locrian ✓
  The scale matches the chord's character: both unstable, both half-diminished
</pre>

<h3>Locrian ♮2 (a Better Option)</h3>
<p>Many jazz players prefer Locrian ♮2 over m7♭5 chords. This is the 6th mode of the jazz melodic minor scale — same as Locrian but with a natural 2nd instead of a flatted 2nd:</p>
<pre>
B Locrian:   B C  D E F G A   (♭2 = C)
B Locrian ♮2: B C# D E F G A   (natural 2 = C#)

The natural 2nd removes the harshest tension and gives more melodic options.
B Locrian ♮2 = 6th mode of D melodic minor.

Both work over Bm7♭5. Locrian ♮2 is warmer; pure Locrian is more angular.
</pre>

<h2>Comparison to Other Dark Modes</h2>

<table>
  <thead><tr><th>Mode</th><th>Formula</th><th>Darkest feature</th><th>Use case</th></tr></thead>
  <tbody>
    <tr><td>Aeolian</td><td>1 2 ♭3 4 5 ♭6 ♭7</td><td>♭6 — melancholic</td><td>Standard minor — rock, classical</td></tr>
    <tr><td>Phrygian</td><td>1 ♭2 ♭3 4 5 ♭6 ♭7</td><td>♭2 — exotic, tense</td><td>Flamenco, metal, exotic colour</td></tr>
    <tr><td>Locrian</td><td>1 ♭2 ♭3 4 ♭5 ♭6 ♭7</td><td>♭5 — unstable tonic</td><td>Half-diminished chords, avant-garde</td></tr>
  </tbody>
</table>

<h2>References</h2>
<ul>
  <li>Levine — <em>The Jazz Theory Book</em></li>
  <li>Bergonzi — <em>Inside Improvisation Series</em></li>
  <li><a href="https://www.jazzguitar.be/blog/locrian-mode/" target="_blank" rel="noopener">jazzguitar.be — Locrian Mode ↗</a></li>
</ul>
