The 'O Antiphons'

In many churches of the western tradition, tomorrow marks the beginning of the "O Antiphons" in the Liturgy of the Hours. For those unfamiliar with these, here is Father William Saunders' fascinating explanation: What are the "O Antiphons"? In the 19th century John Mason Neale translated and adapted them as the beloved Advent hymn, O Come, O Come Emmanuel. (Hat tip: Mere Comments)