The traditional service for Wednesday night before Maundy Thursday is known as Tenebrae. Services vary among denominations, but most of them feature the gradual extinguishing of lights in the sanctuary until the service ends in total darknesss. This night marks the beginning of the end, the descent into despair that will be miraculously lifted by the dawn of Easter.
The music for these services often consists of settings of texts from the Lamentations of Jeremiah. A few examples: