The principal Tenebrae ceremony is the gradual extinguishing of candles upon a stand in the sanctuary called a hearse….
Six altar candles are put out during the Benedictus, gradually reducing also the lighting in the church throughout the chanting of the canticle. Then any remaining lights in the church are extinguished and the last candle on the hearse is hidden behind the altar, ending the service in total darkness. The strepitus (Latin for “great noise”), made by slamming a book shut, banging a hymnal or breviary against the pew, or stomping on the floor, symbolizes the earthquake that followed Christ’s death, although it may have originated as a simple signal to depart. After the candle has been shown to the people, it is extinguished, and then put “on the credence table,” or simply taken to the sacristy. All rise and then leave in silence. — Tenebrae