A Dictionary of Music and Musicians/Phrygian Mode
PHRYGIAN MODE (Lat. Modus Phrygius; Modus mysticus). The Third of the Ecclesiastical Modes. [See Modes, the Ecclesiastical.]
The Final of the Phrygian Mode is E. Its range extends upwards, in the Authentic form, from that note to the Octave above; and Semitones occur between its first and second and fifth and sixth Degrees. Its Dominant is (B, the fifth Degree of the Scale, being inadmissible, on account of its false relation with F). Its Mediant is G; and its Participant A, for which note B is sometimes substituted. Its Conceded Modulations are D (the note below the Final), and F; and its Absolute Initials, E, F, C, and, more rarely, G. Its principal features are shewn in the subjoined example.
In its Plagal, or Hypophrygian form (Mode IV, Modus Hypophrygius or Harmonicus), its range lies a Fourth lower, extending from B to the F Octave above. In this form, the Semitones lie between the first and second, and the fourth and fifth Degrees. The Dominant of the Hypophrygian Mode is A. Its Mediant is G, and its Participant C, for which note F is sometimes substituted. Its Conceded Modulations are D and (the lowest note of the Mode). Its Final, like that of the Authentic form, is E. The genera conformation of the Mode is shown in the subjoined example.
It will be observed that the compass and intervals of this Mode correspond exactly with those of the rejected Locrian; yet Hypophrygian Melodies have always been considered perfectly lawful. The reason is, that the Locrian Mode, being Authentic, is subject to the Harmonic Division, which produces a Quinta falsa between B and F, and a Tritonus between F and B: whereas, the Hypophrygian Mode, being Plagal is subject to the Arithmetical Division, and exhibits a Perfect Fourth, between B and E, and a Perfect Fifth, between E and B. [See pp. 341–342 of this volume.]