Locrian

A mode without a tonic

Stack thirds on the first degree and you get a diminished triad: B D F in B Locrian. Every other diatonic mode has a stable major or minor chord on its first degree; this one does not, so nothing in it can function as a resting point and the ear keeps looking elsewhere for home.

That is why Locrian is described as theoretical more often than any other mode. It exists as the seventh mode of the major scale by construction, but music written in it has nowhere to settle, and attempts to use it as a key usually end up sounding like an exercise in avoiding resolution.

What it is actually used for

Over a half-diminished chord it is the standard choice, and that is where most working musicians meet it: the two chord of a minor two-five-one is half-diminished, and Locrian supplies its scale. In that context nobody is playing in the mode; they are playing over one chord for two bars.

The variant most players eventually prefer there is Locrian natural two, from the melodic minor family, which raises the flattened second by a semitone. It fits the same chord and sounds considerably less bleak, because the note directly above the root is no longer a semitone away.

Where it turns up as a colour

Metal uses it for the same reason it uses Phrygian, usually over a pedal note and rarely for long. Some contemporary composition treats the instability as material rather than as a problem, letting it prevent closure across a whole section.

Outside those cases it appears mostly as a passing region rather than a destination: a bar or two on the way somewhere, where its lack of gravity is the point.

What it is confused with

Phrygian, which shares the flattened second but keeps a perfect fifth and therefore has a stable minor tonic chord. The test is the fifth degree: if the tonic chord is minor you are in Phrygian, if it is diminished you are in Locrian.

The other confusion is with the half-whole diminished scale, which also fits unstable chords but is symmetric, has eight notes and belongs to a different family altogether.

The rest of the family

Locrian is the seventh mode of the major scale, so B Locrian and C major share the same notes. Its immediate neighbour is Aeolian, two degrees away in construction but a world away in stability, and comparing the two from the same root shows exactly how much work a perfect fifth does.

Frequently asked questions