Isaac's Virgo prudentissima, composed in 1507 for the Reichstag in Constance that confirmed Maximilian I as Holy Roman Emperor, is one of the composer's most complex and extended works. It is also a self-consciously constructivist piece that looks back to the repertoire of tenor motets pioneered by Guillaume Du Fay, Jehan de Ockeghem, and most prominently by Iohannes Regis. Yet its construction is markedly different from similar motets by his contemporary Josquin Des Prez, who used a nearly schematic construction in Miserere mei Deus, and ostinato techniques in Illibata Dei genitrix. This article takes a close look at Virgo prudentissima in order to show how Isaac achieves both a great deal of variety in textures and sonorities and a remarkable degree of motivic and thematic unity in the piece. The unity in Isaac's motet is largely due to an interplay of two basic textures and two kinds of motivic construction that are exposed in the first few sections of each pars and then fused in the concluding section, and to a judicious choice of which phrases of the cantus firmus—an antiphon for Vespers of the Assumption—he chooses to paraphrase in the free voices.
The motet's mensural structure—one section with all voices in 𝇈, and one with the tenor continuing in ▮ but the other five voices switching to 𝇈2, with semibreve-minim equivalence with the tenor—has been ignored entirely in all modern performances of the work that have been recorded in the last thirty years, usually with disastrous consequences for the performance of the secunda pars of the work. Isaac's notation is implausible until one realizes that he is using it for symbolic purposes and at the same time pointing to a correct tempo relationship between the partes by his organization of the phrase structure and the imitation at the beginning of the secunda pars. Isaac thus places this motet in what can be called a mensural tradition, which has its beginnings in the motets of Du Fay in the 1430s and in the wholesale adoption of the “English” relationship between triple and duple meters in the second half of the fifteenth century.
Thomas Binkley in memoriam
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