[2][3] The name first came into use in modal chant theory after the 18th century,[2] when Locrian was used to describe the newly-numbered mode 11, with its final on B, ambitus from that note to the octave above, and with semitones therefore between the first and second, and between the fourth and fifth degrees.
For example, the tonic triad of B Locrian is made from the notes B, D, F. The root is B and the dim 5th is F. The diminished-fifth interval between them is the cause for the chord's striking dissonance.
The Greeks used the term "Locrian" as an alternative name for their "Hypodorian", or "common" tonos, with a scale running from mese to nete hyperbolaion, which in its diatonic genus corresponds to the modern Aeolian mode.
[7] In his reform of modal theory,[8] Glarean named this division of the octave "hyperaeolian" and printed some musical examples (a three-part polyphonic example specially commissioned from his friend Sixtus Dietrich, and the Christe from a mass by de la Rue), though he did not accept hyperaeolian as one of his twelve modes.
[9] The use of the term "Locrian" as equivalent to Glarean's hyperaeolian or the ancient Greek (diatonic) mixolydian, however, has no authority before the 19th century.