"Elusive and mysterious," "special sound world," "the Sphinx among Obrecht's masses" -- these are the phrases scholars try to attach to the Missa Maria zart, which indeed stands alone among the works of Jacob Obrecht. Taking over an hour to perform, this piece weighs in as the longest mass setting of the Renaissance, and must be heard in its entirety for the complete experience -- an oceanic wash of undulating polyphony which no written words could encompass.
This Mass takes as its cantus firmus a Tyrolian song of Marian devotion, apparently dating from around 1500. Instead of placing complete statements of the preexistent melody in each movement, Obrecht uses his characteristic segmentation technique upon it, dividing the melody into twelve pieces, which are apportioned sequentially across the entire Mass. When segments are repeated, they are subject to a vast array of mensural transformations; at times the augmentation stretches to as much as 12 times the original note values! In the Agnus Dei, the entire melody is finally heard complete, as a summation or recapitulation: in the Bass in Agnus I, migrating among the three voices of Agnus II, and magnificently in the upper voice in Agnus III. This technique, common to several of his mature mass settings, yields a sense of large-scale process to the entirety of the five movements.
But such an account of the structure gives no concept of the kaleidescopic tapestry of sound resulting from the inexhaustible spinning-out of the voices. Long sections of musical text derive from antiphonal interplay of fragmentary motives, or manipluations which vary the rhythmic transformation within a melodic statement; the list of surface devices saturating the musical fabric with the melody could go on and on.
The musical impregnation also goes beneath the surface. For instance, clever scholarship has discovered hidden structure to the apparently "free" trio setting the text "et incarnatus est": the Bass voice, if all notes except the semibreves (half notes) are removed, contains the first half of "Maria zart," and the upper voice the second half in like manner. One scholar has even gone to great lengths to uncover a deep numerological subtext to the Mass.
Some of this speculation is driven by the piece's unique length and depth of sonic discourse. No liturgical occasion comes easily to mind which would require such music to be written in the fifteenth century. Perhaps, then, a more personal explanation could be sought. Obrecht, though aging, could not have predicted his immanent death of the plague. Nonetheless, one can readily imagine a musical testament by a composer at the height of his powers, set to an affective devotional song, which concludes, "Am lezten End, bitt, dich nit wend von mir in meinem Sterben" (At the final end, pray, turn not from me in my death).