Locrian

What it means

The Locrian mode runs on the natural notes from B to B. Its semitone steps lie between the first and second and between the fourth and fifth degrees. Characteristic, and at the same time problematic, is that above the tonic lies not a perfect but a diminished fifth — the tritone thus stands in the place where otherwise the supporting framework of the mode would be.

Musical use

Precisely this explains why this mode did not occur in early practice. A chant that closes on this note does not sound concluded, because the supporting fifth sonority is missing. In the order of the church modes it is therefore not included; it appears only in later theoretical accounts that count through the system of modes completely.

It has practical significance nonetheless, namely in connection with a chord: the triad above its tonic is diminished, and with an added minor seventh the half-diminished seventh chord results. This stands in minor on the second degree and leads to the dominant; in jazz harmony the Locrian scale belongs as the note stock to this chord.

Locrian is to be distinguished from Phrygian, which it resembles in the lowered second degree; the difference lies in the fifth, which there is perfect and here diminished. This one note decides whether the scale has a centre.

In modal jazz theory, Locrian is played over the half-diminished seventh chord.

Other names

Locrian is the English designation of the same mode and is common in jazz textbooks, where the Locrian scale is played over half-diminished seventh chords. The English note names differ: B corresponds to the German H, so the Locrian mode on the natural notes begins on “B” in English usage and on H in German usage.

Performance practice

Do not practise the Locrian scale in isolation but over the associated half-diminished seventh chord — there it becomes meaningful, alone it remains without orientation. Watch the diminished fifth: it is the note that shapes the scale, and it wants to be carried onward.