plagal

[pley-guh l] /ˈpleɪ gəl/
adjective, Music.
1.
(of a Gregorian mode) having the final in the middle of the compass.
Compare authentic (def 5a).
Origin
1590-1600; < Medieval Latin plagālis, equivalent to plag(a) plagal mode (apparently back formation from plagius plagal; see plage) + -ālis -al1
Examples from the web for plagal
  • The second, fourth and second plagal tones all use the soft chromatic scale.
British Dictionary definitions for plagal

plagal

/ˈpleɪɡəl/
adjective
1.
(of a cadence) progressing from the subdominant to the tonic chord, as in the Amen of a hymn
2.
(of a mode) commencing upon the dominant of an authentic mode, but sharing the same final as the authentic mode. Plagal modes are designated by the prefix Hypo- before the name of their authentic counterparts: the Hypodorian mode
Compare authentic (sense 5)
Word Origin
C16: from Medieval Latin plagālis, from plaga, perhaps from Greek plagos side
Word Origin and History for plagal
adj.

1590s, from Medieval Latin plagalis, from plaga "the plagal mode," probably from plagius, from Medieval Greek plagius "plagal," in classical Greek "oblique," from plagos "side" (see plagio-).