Gregorian melodies … consist of a loose, almost accidental arrangement of tones which is, strictly speaking, valid in each case only for the particular type of melody, for the particular constellation of tones being considered. Thrasybulos Georgiades, Music and Language… (1974), 12.
Modality in Renaissance music is a complicated issue, involving intellectual and religious factors such as a renewed interest in the theoretical writings of classical antiquity and the Middle Ages, and the powerful role the Catholic Church played in the lives of composers. Four pairs of modes were used in the setting of chant, probably borrowed from early Byzantine Christianity. Each pair consisted of an authentic and a plagal mode with the same final (our modern “tonic”). The original untransposed, or natural, modal pairs began on D, E, F, and G; authentic modes had a higher ambitus, or range, than plagal modes.
By the 16th century, modal theory and contrapuntal practice had grown apart to some extent and a good deal of the theoretical writing of the period worked hard to make modality a vivid compositional issue once again. There was much discussion of the relationship between each mode and particular emotions or affective situations attached to each mode, acknowledged since the time of Plato and, later, Boethius; however, there is little evidence that text expression through the choice of a specific mode was often a serious pre-compositional issue.
Since the modes were originally applied to monophonic music (chant, for example), theorists of the Renaissance were hard pressed to claim classical or medieval authority for applying the modes to the polyphonic music of their time.
Our work in species counterpoint will use six modes recognized by late 16th-century composers and theorists. The Aeolian and Ionian modes — our modern natural minor and major scales, respectively — were added to the system by Swiss theorist-poet Henricus Glareanus in his seminal treatise Dodecachordon (literally,”12-stringed instrument,” a metaphor for the new system of 12 modes (6 authentic, 6 plagal), completed in 1547).
Sing these modes, play them, and memorize their intervallic characteristics.
1) Memorize the names, placement, and interval structure of each of the six diatonic authentic modes.
2) Sing each mode aloud using scale or modal degrees (1, 2, 3…etc.) and then letter names (D, E, F…)
3) Using your own music manuscript paper (MS paper), transpose each authentic mode down a 5th, and then down a 5th again. What do you notice about accidentals?