Beata viscera is a song of wonder at the womb of Mary. It comes from Pérotin, a master of the Notre-Dame school in Paris around the year 1200, when the great cathedral was still rising around its singers.
Blessed is the womb of the Virgin Mary, at whose breast the King of great renown, hiding his divine power in another garment, set down the covenant of God and humankind.
The verses keep turning the same mystery over: the infinite making itself small enough to be carried, heaven consenting to be born. It is sung slowly, one voice walking through the words, with long breaths where the stone answers back.