For the most part Isaac hid the dance tune behind a thicket of paraphrase and polyphony. But all at
once the second Agnus Dei gives away the game. Convention decreed that this middle section of the last
part of the Mass Ordinary be cast as a “tenor tacet” setting, in three voices, and so it is. But very
whimsically and unconventionally, Isaac transferred the tenor tune to the bassus voice, where it is laid out
in a series of even breves just as it would be in a bassadanza collection. And it is accompanied by the
superius and the altus in a polyphony so rough and ready—glorified antiphony, hocket-like exchanges,
sequences that track the tenor down the scale—that it simply has to be a sly send-up of an actual alta
capella, caught in the act of improvising, perhaps even drawn “from life” (Ex. 15-10).
FIG. 15-9 Loyset Liedet, Ball at the Court of King Yon of Gascony (Paris, Bibliothèque de l’Arsenal, Manuscripts Français 5073,
fol. 117v).
Ortiz provides six different recercadas over the Spagna tenor, the idea being that after having
mastered them the pupil can then go on to make up his own. Ex. 15-11 shows the beginnings of all six.
This is another way in which the written can suggest to us the unwritten, although Ortiz was not training
anyone in the art of dance accompaniment. Like virtuosos both before and after him, in a tradition that
continues to this day, he appropriated a sublimated dance style—dance music, not for active dance use but
for receptive listening—as his vehicle for a display of dexterity.
EX. 15-10 Henricus Isaac, Missa super La Spagna, Agnus II