Isaac’s mastery of cantus firmus polyphony is on full display as he sets the traditional opening chant for Christmas. The chant is echoed in all voices but is carried throughout in the tenor even though the incipit is in the soprano. Rhythmically, this is not a terribly challenging motet, but its charm comes in its beautiful phrases and harmonies. Based on Psalm 98, the lyrics reference God’s oversight of the Earth.
Puer natus est nobis et filius datus nobis. Cujus imperium super humerum ejus et vocabitur nomen ejus, magni consili Angelus. Cantate Domino canticum novum quia mirabilia fecit
Unto us a child is born and to us a son is given. Dominion is on His shoulder and His name shall be called the Angel of Great Counsel. Sing unto the Lord a new song for He has done marvelous things.
Viderunt omnes fines terrae salutare Dei nostre.
All the ends of the earth have seen the salvation of our God.