Locrian Mode - Overview

Overview

The Locrian mode is the only modern diatonic mode in which the tonic triad is a diminished chord, which is considered dissonant. This is because the interval between the root and fifth of the chord is a diminished fifth. For example, the tonic triad of B Locrian is made from the notes B, D, F. The root is B and the fifth is F. The diminished-fifth interval between them is the cause for the chord's dissonance. Although in some practices, the fifth may be omitted from the tonic chord.

The name "Locrian" is taken from music theory of ancient Greece. However, what is now called the Locrian mode was what the Greeks called the Diatonic Mixolydian tonos. 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. In his reform of modal theory in the Dodecachordon (1547), Heinrich 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 Pierre de La Rue), though he did not accept Hyperaeolian as one of his twelve modes. The usage of the term "Locrian" as equivalent to Glarean's Hyperaeolian or the ancient Greek (diatonic) Mixolydian, however, has no authority before the 19th century.