from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Music Of or being a medieval mode having a range from the fourth below to the fifth above its final tone.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Designating a mode lying a perfect fourth below the authentic form.
- adj. Designating a cadence in which the subdominant chord precedes the tonic.
from the GNU version of the Collaborative International Dictionary of English
- adj. Having a scale running from the dominant to its octave; -- said of certain old church modes or tunes, as opposed to those called
authentic, which ran from the tonic to its octave.
from The Century Dictionary and Cyclopedia
- In Gregorian music, noting a mode or melody in which the final is in the middle of the compass instead of at the bottom: opposed to authentic. See mode
- In modern music, noting a cadence in which the chord of the tonic is preceded by that of the subdominant. See cadence.
_perfect plagal cadence_, the last two are _imperfect plagal_.
Final cadences often have short plagal extensions, with pedal notes normally occurring only at these places, often in the top voice.
These “irregularities” in the treatment of the mode do not, however, infringe the rules laid down by Tinctoris in his treatises: each voice respects its own modal unity but, in addition, the combination of the first and second modes in their irregular forms creates a mixture of authentic and plagal which Tinctoris as theoretician allows.
The Beatles incorporated classical elements into rock so seamlessly that it is easy to forget that string quartets and Bach-like countermelodies and bass lines (not to mention plagal cadences) did not always populate pop.
But they both heard the bittersweet longing within the plagal cadence, and chose their vocabularies accordingly.
You know who else used to stack his harmonies heavily towards the plagal, the flat side of the circle of fifths?
The subdominant, which we all know and love from plagal "Amen" cadences, colors much of gospel harmony.
The juxtaposed melodic phrases extend over an ambitus, or compass of the whole of the fifth and two tones of its plagal, or the sixth mode.
Thomas Riis is the Joseph Negler Professor of Music at the University of Colorado at Boulder, and, as you'll have gathered, his is a scholar's approach -- heavy on the tonic pitches and plagal effects and ostinatos.
For future reference, the Phrygian mode has that distinctive minor 2nd, and should not be confused with the “Hypophrygian” plagal mode.