Locrian mode

The Locrian mode is either a musical mode or simply a diatonic scale.

Locrian is the word used to describe the inhabitants of the ancient Greek regions of Locris. Although the term occurs in several classical authors on music theory, including Cleonides (as an octave species) and Athenaeus (as an obsolete harmonia), there is no warrant for the modern usage of Locrian as equivalent to Glarean's Hyperaeolian mode, in either classical, Renaissance, or later phases of modal theory through the 18th century, or modern scholarship on ancient Greek musical theory and practice. The name first came to be applied to modal chant theory after the 18th century, when it was used to describe the mode newly numbered as mode 11, with final on B, ambitus from that note to the octave above, and with semitones therefore between the first and second, and fourth and fifth degrees. Its reciting tone (or tenor) is G, its mediant D, and it has two participants: E and F. The final, as its name implies, is the tone on which the chant eventually settles, and corresponds to the tonic in tonal music. The reciting tone is the tone around which the melody principally centres, the mediant is named from its position between the final and reciting tone, and the participant is an auxiliary note, generally adjacent to the mediant in authentic modes and, in the plagal forms, coincident with the reciting tone of the corresponding authentic mode.

In modern practice, the Locrian may be considered to be a minor scale with the second and fifth scale degrees lowered a semitone. The Locrian mode may also be considered to be a scale beginning on the seventh scale degree of any Ionian, or major scale. The Locrian mode has the formula 1, ♭2, ♭3, 4, ♭5, ♭6, ♭7. Its tonic chord is a diminished triad (Bdim in the Locrian mode of the diatonic scale corresponding to C major). This mode's diminished fifth and the Lydian mode's augmented fourth are the only modes to have a tritone above the tonic.

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