"" (A boy is born for us) is a Gregorian chant, the introit for Christmas Day. Thomas Tallis wrote a Christmas mass on the chant.
The text of the antiphon is taken from Isaiah 9:6, while the psalm verse is verse 1 from Psalm 98, "Sing a new song to the Lord". -->}}
The melody was used by composers in contrafacta such as the Christmas mass by Thomas Tallis.