votive service but a cathedral Mass attended by dignitaries and magnates in force (precisely the kind of
stellar occasion, in short, for which isorhythmic motets used to serve).
As in Leonel’s Mass, the cantus firmus of one “movement” is (with minor variables like rests between
phrases) the cantus firmus of all. Each “movement” has the same overall bipartite structure articulated
through the same contrast of perfect and imperfect mensurations. But each mensuration governs a full
statement of the enormous cantus firmus, so that each “movement” embodies a double cursus of what is
already a very lengthy melody. So this Mass would be twice as long as Leonel’s even if the apparently
missing (and probably heavily trooped) Kyrie from Leonel’s Mass were restored.
In fact it is surely more than twice as long, because the “ideal” structure of this or any cyclic Mass
(that is, the structure as composed) is not necessarily the same as its practical structure (the structure as
performed). The two sections of the Kyrie from the Caput Mass are composed—“Kyrie” in perfect time
and “Christe” in imperfect—to satisfy the requirements of its structural plan. But they do not satisfy the
requirements of the liturgy. In the actual liturgical performance of any Mass the words “Kyrie eleison”
must be repeated following the words “Christe eleison”; and so we may assume that in the liturgical
performance of this Mass, either the missing words were shoehorned into the “Christe,” or the first
section was performed da capo in order to complete the liturgical text.
FIG. 12-5 Salisbury Cathedral, home of the Sarum chant, the repertoire that included the Caput melisma.
But however impressive, length is not the most important dimension in which the Missa Caput has
been magnified over and above its predecessors. More significant by far, historically speaking, is the
amplification of the texture. The complement of voices has been increased to four—and that number of
voices, in precisely the configuration found in this Mass, became the norm for a century or more of intense
Mass Ordinary composition. Once something becomes normal it is quickly taken for granted; so let us
seize this moment, while things we have long since taken for granted are still in the process of being
formed, to witness the birth of “four-part harmony.”
The Caput tenor is an unusually high-lying chant, making repeated ascents to the G that in the old
eight-mode system was the highest theoretically recognized “scale note” of all. The original melisma is
given in Ex. 12-4b for comparison with the tenor of the Kyrie, a portion of which is shown in Ex. 12-4a.
The tenor’s high tessitura puts it in a range far closer to, and apter to cross with, the contratenor above it