A Dictionary of Music and Musicians/Mixed Modes
MIXED MODES. Writers on Plain Chaunt apply this term to tonalities which embrace the entire compass of an Authentic Mode, in combination with that of its Plagal derivative: thus, the Mixed Dorian Mode, extends from A, to the next D but one above it; the Mixed Phrygian, from B, to the next E but one; the Mixed Lydian, from C, to the next F but one; and the Mixed Mixolydian, from D, to the next G but one. [See Maneria.]
A very fine example of Mixed Mixolydian, (Modes VII and VIII, combined), is to be found in the Melody of 'Lauda Sion.' [See Lauda Sion.]
Polyphonic Music for unequal Voices is always, of necessity, written in Mixed Modes: since, if the Treble and Tenor sing in the Authentic Mode, the Alto and Bass will naturally fall within the compass of its Plagal congener; and, vice versa. The Composition is, however, always said to be in the Mode indicated by its Tenor part.[ W. S. R. ]