Locrian Mode
Locrian is a minor scale with both its second and its fifth degrees flattened. The flattened fifth is the structural one: it makes the chord built on the tonic a diminished triad, so the mode has no stable home chord to rest on.
Degrees: 1 ♭2 ♭3 4 ♭5 ♭6 ♭7
C Locrian
Unstable by construction. It is the least used mode precisely because its own tonic chord will not sit still, which makes it a passing colour over a half-diminished chord rather than a key to write in.
Characteristic tones: ♭5 (G♭), ♭2 (D♭)
The flat fifth, with the flat second close behind. Flattening the fifth is what makes Locrian structurally different from every other mode rather than merely darker: the tonic triad is diminished, so the mode has no stable home chord to rest on.
On a keyboard
Two octaves from middle C. Every key belonging to the scale is filled; the tonic is aubergine and the characteristic tone is rose-gold.
On a guitar neck
Every position of every scale note, open strings through fret 15. Scroll sideways on a phone to reach the upper frets.
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Why the flat fifth changes everything
Every other mode of the major scale has a perfect fifth above its tonic. That interval is what makes a tonic feel like a tonic — it is the strongest consonance after the octave, and it is the interval the overtone series reinforces most directly. Locrian is the one mode without it.
The consequence is not a shade of darkness but a structural absence. The triad built on the first degree is diminished, and a diminished triad is a chord in transit; it exists to move somewhere. A mode whose tonic chord cannot sit still cannot really function as a key, which is why Locrian is described as the least-used mode rather than as a rarely-chosen one. It is not a matter of taste.
Where it is genuinely used
The honest answer is: over one chord, briefly. Extend the Locrian tonic triad to a seventh and you get a half-diminished seventh chord — root, minor third, diminished fifth, minor seventh — and that chord has a real and frequent job. It is the second-degree chord of every minor key, the opening chord of the minor two-five-one progression that underpins a very large amount of jazz repertoire.
So Locrian is the scale a player reaches for over that chord, for the bar or two that it lasts, before the harmony moves on. Used that way it is not exotic at all; it is simply the set of notes that fits a chord that appears constantly. What it is not is a key signature you would write a piece in.
The variant that is easier to use
Improvisers frequently substitute a related scale here, and it is worth knowing why. Locrian's flattened second sits a semitone above the tonic, which clashes with the chord's root in a way that is hard to make sound intentional over a passing chord.
Raising that second degree gives Locrian natural 2, the sixth mode of melodic minor. It keeps the flattened fifth that fits the chord and removes the interval that fights the root. If you have heard players describe Locrian as unusable and then heard the same players comfortably improvising over half-diminished chords, this substitution is usually what is happening.
Finding it, and hearing it fairly
Any Locrian scale uses the notes of the major scale a semitone above its tonic: B Locrian is the notes of C major started on B, which on a piano makes it the white notes from B to B. That is the cheapest possible way to hear it — no accidentals, no new fingering.
But play it over a B bass note and it will sound unresolved, because it is. To hear the mode doing its actual job, play those same notes over a half-diminished seventh chord rooted on B instead, and then let the chord move on to an E dominant seventh and an A minor. In that context the scale stops sounding like a failed key and starts sounding like what it is: the correct set of notes for one chord in a progression that is going somewhere.
The seven chords this mode harmonises into
Stack thirds on each degree of the scale and you get these. Read from left to right, they are the chords available to a piece written in the mode.
| Degree | 1 | ♭2 | ♭3 | 4 | ♭5 | ♭6 | ♭7 |
|---|---|---|---|---|---|---|---|
| Roman numeral | i° | ♭II | ♭iii | iv | ♭V | ♭VI | ♭vii |
| Quality | diminished | major | minor | minor | major | major | minor |
Questions people ask about Locrian
- Why does Locrian sound unresolved no matter what I play?
- Because its tonic triad is diminished. The flattened fifth removes the interval that makes a root note feel like a home, so there is nothing in the scale for a phrase to land on and stay.
- Which chord does Locrian actually fit?
- The half-diminished seventh chord, written m7♭5 — root, minor third, flattened fifth, minor seventh. All four of those notes come straight out of the Locrian scale on the same root.
- Is Locrian the darkest mode?
- On the usual brightness ordering — Lydian, Ionian, Mixolydian, Dorian, Aeolian, Phrygian, Locrian — yes, it sits at the dark end. But it is different in kind from the others rather than just further along, because it is the only one that loses the perfect fifth.