Josquin was one of the greatest Renaissance composers, & surely among the most progressive. This piece begins with a few strikes of metallic percussion which serve to prepare & to tone dramatically. After that, the music is simultaneously dark & spiritual. Most early contrapuntal composers had the problem of being directed in their music by where the notes could go; Josquin told the notes what he wanted them to do, & they did it. The way he sets up melodic directions, expectations, follow-through & reaction here is wonderful. Of all the great work he did in his life, it's fair to call this his most monumental piece.