Tuesday, April 26, 2011

Writing in Locrian

In modern Western music, the Locrian mode is built from the seventh degree of the major scale (at a piano, you could start on B and play only the white keys). In this mode, the tonic triad is diminished. This makes it very difficult (or even, according to traditional phrasing practice, impossible) to write in this mode without the result sounding like it's actually in a different key.

The tonic must be continually reasserted as the center, which is challenging because a diminished chord is quite dissonant and does not sound like a place of rest. This chord can be made more manageable, though less distinctly Locrian, by omitting its fifth degree and adding a minor seventh; another option is to "cheat" by raising the fifth degree chromatically only for the tonic chord. In either case, to define a Locrian identity, the modified tonic chord would require balance from the iii and V chords in proper diatonic form, where the true fifth degree of the mode can be voiced more comfortably.

If the fifth degree is raised permanently, the mode becomes Phrygian. This change makes the iii chord major, but more importantly, the V chord becomes diminished, which can be nearly as troublesome as a diminished tonic chord. In both Locrian and Phrygian, the second, third, sixth, and seventh degrees are all minor; they can sound even darker than the Aeolian mode, otherwise known as the natural minor scale, which has a major second. If the pattern of whole- and half-steps in the Locrian mode (HWWHWWW) is reversed, the result is the Lydian mode, which is completely major but features an augmented fourth.

Due to the difficulties inherent in working with the Locrian mode, it has always been extremely uncommon, though a few composers have made use of it. Claude Debussy exhibits the mode in three passages of his last orchestral work, Jeux. It can be done!

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