Commissioned in 2003 by the Song Company, the O Antiphons, also known as The great Os are Magnificat antiphons used at Vespers of the last seven days of Advent in Western Christian traditions. They are referred to as the “O Antiphons” because the title of each one begins with the vocative particle “O”. Each antiphon is a name of Christ, one of his attributes mentioned in Scripture.
The 4th O Antiphon for December 20, “O Clavis David” (Oh key of David) is drawn from Isaiah 9:6 and 22:22.
O Clavis David