Authentic mode[edit]The authentic m

Authentic mode[edit]
The authentic modes were the odd-numbered modes, 1, 3, 5, 7, and this distinction was extended to the Aeolian and Ionian modes when they were added to the original eight Gregorian modes in 1547 by Glareanus in his Dodecachordon (Powers 2001a). An authentic mode has its final as the lowest note of the scale, though in modes 1, 3, and 7 it may occasionally descend one note further, in which case this added scale degree is called the "subfinal" which, since it lies a whole tone below the final is also the "subtonium" of the mode. The range of mode 5 (Lydian) does not employ a subfinal, and so always maintains the note F as its lower limit (Powers 2001d). These four modes correspond to the modern modal scales starting on D (Dorian), E (Phrygian), F (Ionian = the Gregorian Lydian), and G (Mixolydian). The tenor, or dominant (corresponding to the "reciting tone" of the psalm tones), is a fifth above the final of the scale, with the exception of mode 3 (Phrygian), where it is a sixth above the final. This is because a fifth above the tonic of mode 3 is the "unstable" B♮/B♭.

The older Byzantine system still retains eight tones (ἦχοι – echoi), each consisting of a small family of closely related modes that, if rounded to their diatonic equivalents, would be the eight modes of Gregorian chant. However, they are numbered differently, the authentic modes being 1, 2, 3, 4 (Anon. n.d.). Other Eastern Christian rites use similar systems of eight modes; see Syriac usage of Octoechos and Armenian usage of Octoechos.