This year’s Good Friday service will follow the traditional liturgy of Tenebrae for Holy Week, with readings from the Psalms and Thomas Tallis’s setting of the Lamentations of Jeremiah.  In the contemplative service of Tenebrae (Latin for “darkness”), music serves as a reflection on the texts being read, and a candle is extinguished after each reading, until only one is left.  Five singers, four drawn from the choir — Megan Sharp, Steve Patek, Jonathan Schakel, and Winston Barham — along with guest Emily Stubbs, will sing music from the Renaissance by Tallis, William Byrd, Giovanni Croce, and Lodovico Viadana.