In the lengthy Gloria and Credo, the cantus firmus gets a double cursus that in its accelerated
repetition behaves more like the tenor of an isorhythmic motet than ever. The speed-up here is
accomplished in two stages: first the accompanying voices go into diminution against the second half of
the tenor tune, and then the tenor itself goes into diminution to join them. In the “Tu solus altissimus,” the
climactic subsection of the Gloria (Ex. 12-13), the whole cantus firmus is sung more or less exactly as
shown in Ex. 12-10 (ut jacet, “as it stands,” to use the contemporary jargon for “at the notated tempo”).
All that differs is the amount of resting between phrases.
“PERVADING IMITATION”
With its vivaciously lilting, hemiola-infested rhythms and its fanciful little patches of voice-exchange on
the “horn call” motif, Busnoys’s “Tu solus” (Ex. 12-13) really crowns the Gloria. Not only its inherent
qualities but also its placement testify to Busnoys’s “art of shapeliness” and justify the high regard in
which his work was held, as well as the dynastic influence it exerted on his contemporaries and juniors.
And yet if we are to take a properly “historical” view of this Mass, it is on the relatively inconspicuous
tenor tacet sections that we must train our lens. They represent a new principle of composing—
exceptional in Busnoys’s time, but standard practice a hundred years later and for centuries thereafter.
EX. 12-13 Antoine Busnoys, Missa L’Homme Armé, Gloria, “Tu solus altissimus”