Plagal mode (from Gk. plagios, Lat. plagalis or plagis)
- Harold S. Powers
Any of the church modes whose Ambitus, or range, includes the octave lying between the 4th below and the 5th above its Final. The term is thus applied to the four even-numbered modes of Gregorian chant (2, 4, 6 and 8), each of which takes its name from the corresponding odd-numbered mode, with the addition of the prefix ‘hypo-’: ...