C-sharp major
Pärt set the piece using the biblical text in the Vulgate version (). He set it in C-sharp minor for a mixed choir a cappella. The climax, on the words "lumen ad revelationem" (a light to reveal), is prepared by a "measured procession of gradually expanding phrases" and happens shifting from C-sharp minor to C-sharp major. A reviewer noted that "gorgeous textures, harmonies and sonorities conjure a feeling of purity and emptiness."