bass (SATB)—and can see how the word tenor, originally the “holding part” (which, in cantus firmus
Masses, it still was), acquired the meaning that has since become standard: a high male range. (For that
meaning to become primary, of course, a further major change was required—one that was still some
centuries away: the substitution of mixed choirs for the all-male schola of the pre-Reformation Christian
church.)
Now that both the range and the term for it have been established, let us take a close look at the bassus
voice in Ex. 12-4a. It occupies a pitch space all its own and behaves in a new harmony-defining way.
Like that of any contratenor, its movement tends to be disjunct—by skips—and it has a newly
standardized role at cadences.
A cadence, we may recall, is defined theoretically as stepwise movement, by the “structural pair”
(cantus and tenor), in contrary motion from an imperfect to a perfect consonance. That criterion is of
course met here—and the original chant melisma is given in Ex. 12-4b just to show how the cantus firmus
had to be modified at the ends of both its cursus in order to secure for the tenor a stepwise, properly
“cadential” fall to the final. At the final cadences, both of the Kyrie and of the Christe, an A is
interpolated in the tenor before the final to correspond with the subtonium F in the superius, preparing the
cadence on G. The two voices make their resolutions in contrary motion, and that is the essential cadence
(Ex. 12-4c).
EX. 12-4C Missa Caput, Kyrie (sung with prosulas), mm. 50–52Anyone who has studied counterpoint knows that the only way two additional voices can be added to
the “imperfect” part of this cadence that will be both consonant with the structural pair and independent of
it (in the sense that they will not be forced to double the “essential motion” of either cantus or tenor at the
cadence) is to have them both sing D. At the resolution of the cadence the D above the tenor remains
stationary, and the D below goes the only place it can—to G, doubling the tenor either at the same pitch or
an octave below, depending on the available range. Because this cadence reinforces the effect of the
tenor’s descent to the final from above, it emphasizes the “authentic” modal ambitus and has a particularly
forceful closing effect. It is conventionally called the “authentic cadence,” probably because of its modal
associations (but as with many terms in current, unambiguous and informal parlance, its etymology has not
been researched, and its pedigree is uncertain).
At any rate, the progression in the bass, from the fifth scale degree (supporting the two “essential”
pre-final tones) to the final, is congruent with what we are accustomed to calling a V–I or dominant–tonic
progression. To call it that is to think of the motion of the lowest part as the essential cadential approach,
and to associate the gesture toward closure with the “dominant” harmony. The question for historians is at
what point such a way of conceptualizing cadences becomes justified (or to put it less prescriptively, at
what point such a conceptualization matches that of contemporaneous musicians and listeners).
However they were conceptualized, such an approach and such a harmony were perceptually a part of