A Dictionary of Music and Musicians/Clausula

by W. S. Rockstro

CLAUSULA. The mediæval name for what is now called a Cadence, or Close.^[1]

The most important Close employed in Polyphonic Music, is the Clausula vera, or True Cadence, terminating on the Final of the Mode. The Clausula plagalis, or Plagal Cadence, is rarely used, except as an adjunct to this, following it, at the conclusion of a Movement, in the form of a peroration. A Close, identical in construction with a True Cadence, but terminating upon some note, other than the Final of the Mode, is called a Clausula ficta, subsidiaria, or media; i.e. a False, Subsidiary, or Medial Cadence. A Clausula vera, or ficta, when accompanied, in the Counterpoint, by a suspended discord, is called a Clausula diminuta, or Diminished Cadence, in allusion to the shortening of the penultimate note, in order to allow time for the suspension and resolution of the dissonance.

Though the Clausula vera is the natural homologue of the Perfect Cadence of modern Music, and may, in certain cases, correspond with it, note for note, it is not constructed upon the same principles for, the older progression belongs to what has been aptly called the 'horizontal system,' and the later one, to the 'perpendicular, or vertical system.'^[2] In the Clausula vera, the Canto fermo must necessarily descend one degree upon the Final of the Mode; the Counterpoint, if above the Canto fermo, exhibiting a Major Sixth, in the penultimate note; if below it, a Minor Third. In the Clausula diminuta, the Sixth is suspended by a Seventh, or the Third, by a Second. In either case, the Cadence is complete, though any number of parts may be added above, below, or between, its two essential factors. The constitution of the Perfect Cadence is altogether different. It depends for its existence upon the progression of the Bass from the Dominant to the Tonic; each of these notes being accompanied by its own fundamental harmony, either with, or without, the exhibition of the Dominant Seventh in the penultimate Chord. But, by the addition of a sufficient number of free parts, the two Cadences may be made to correspond exactly, in outward form, through the joint operation of two dissimilar principles; as in the following example, in which a Clausula vera, represented by the Semibreves, is brought, by the insertion of a Fifth below the penultimate note of the Canto fermo, into a form identical with that of the Perfect Cadence.

A Close, formed exactly like the above, but terminating upon the Mediant of the Mode, is called a Clausula media.^[3] In like manner, a Clausula ficta, or subsidiaria, may terminate upon the Dominant, or Participant of the Mode, or, upon either of its Conceded Modulations.^[4] Modern writers are generally inclined to describe Closes of this kind as True Cadences in some new Mode to which the composer is supposed to have modulated. But, the early Polyphonist regarded them as False Cadences, formed upon certain intermediate degrees of the original Mode, from which he was never permitted to depart, by the process now called Modulation.

The form of Clausula plagalis most frequently employed by the Polyphonists was that in which, after a Clausula vera, the last note of the Canto fermo was prolonged, and treated as an inverted Pedal-Point. It is used with peculiarly happy effect in Mode IV—the Plagal derivative of the Phrygian—in which the impression of a final Close is not very strongly produced by the Clausula vera.

The Dominant of this Mode is the fourth degree above its final, corresponding with the modern Sub-dominant. And, as this forms so important an element in the treatment of the inverted Pedal, modern Composers apply the term Plagal to all Cadences in which the Subdominant precedes the Tonic Bass. The term serves its purpose well enough: but it rests upon an erroneous basis, since there is no such interval as a Sub-dominant in the Plagal Modes from which the progression derives its name.

In all the Clausula hitherto described, the two essential parts form together, in the final note, either an Octave, or Unison. There is yet another class in which the parts form a Fifth.

Morley^[5]seems inclined to class these among the True Closes; but most early writers regard them as Clausulæ fictæ, vel irregulares.

[ W. S. R. ]

1. It Is necessary to be very cautions in the use of these two English words, which, in the 16th century, were not interchangeable. Morley, for instance, at pp. 73 and 127 of his Plaine and Easie Introduction (2nd Edit. 1608) applies the term ' Close ' to the descent of the Canto fermo upon the Final of the Mode; and 'Cadence' to the dissonance with which this progression is accompanied, in the Counterpoint, when the form employed is that known as the Clausula diminuta. In cases like this, it is only by reference to the Latin terms that all danger of misconception can be avoided.
2. See vol. i. p. 672 b.
3. For a Table of Medial Cadences in all the Modes, see vol. ii. pp. 243–4.
4. See vol. ii. p. 342.
5. Plaine and Easie Introduction, p. 74 (2nd edition, 1608).