Mode

Modal theory and practice have evolved and changed over centuries, such that the meaning of the idea has shifted with the times. In contemporary practice, mode refers either to (1) a rotation [Page 703]of the tones of a major scale, such that each mode begins on a different scale degree, resulting in a different arrangement of whole and half steps; or (2) a descriptive term for the difference in quality between major and minor keys (e.g., the major mode or minor mode). The names used for the modes today derive from those described by Boethius in the early 6th century, but the scales are not the same. Examples of modal compositions may be found in ecclesiastical chant and pretonal vocal polyphony, as well as in 20th and 21st century art music, folk music, rock, and jazz. In addition to the medieval and Renaissance modal systems, other uses of the term mode include the rhythmic modes of the 13th century and 20th century composer Olivier Messiaen's “modes of limited transposition.”

Six modes are typically employed in contemporary musical practice (the Locian mode is rarely used). Composers and performers freely transpose these modes to other starting pitches. In jazz practice, the modes are a resource for improvisation. (See Table 1).

Table 1 Modes employed in contemporary musical practice

These modes may also be conceptualized (ahistorically) as variants of the familiar major and minor scales. In this scheme, three modes may be heard in relation to the major scale and four to the natural minor scale. (See Table 2).

Table 2 Modes heard in relation to the major and natural minor scales

Descriptions of the modes in the Middle Ages dervied from the Gregorian chant repertoire. Each mode was described by its pattern of whole and half steps in relation to the chant's final pitch, as well as the range of the melody around this final. By the end of the 9th century, modes were identified as authentic or plagal. Authentic modes (e.g., Dorian and Phrygian), had a range with boundary tones that included the final. Plagal modes (e.g., Hypodorian and Hypophrygian) had a range with boundary tones a fourth below the final. This produced a system of eight modes: authentic and plagal modes with a final of D, E, F, and G. Each mode was thought to express a different ethos or affect. Sources from the 11th century, for example, list the Dorian mode as “serious or noble,” Hypodorian as “mournful,” Phrygian as “excited or leaping,” and Hypophrygian as “moderate or lingering.” Although musical practice evolved in the intervening years, it was not until the 16th century that the 8-mode system was expanded to 12 by adding an authentic and plagal [Page 704]mode on C and A, as codified in Heinrich Glarean's Dodecachordon.

Rhythmic modes were the first type of rhythmic notation developed in Western music. Much information about the system comes from a treatise by Johannes de Garlandia (ca. 1250), which describes early polyphony of the Notre Dame School. Each of his six modes outlined a rhythmic pattern of long (L) and short (S) durations to be repeated for the notes of the melody. For example, Mode 1 was L S L S L, Mode 2 was S L S L S, and Mode 3 was L S S L. The mode was indicated to the singer by the way that pitches were grouped together in their notation (by joined noteheads called “ligatures”).

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