The seven O Antiphons (also called the "Greater Antiphons" or "Major Antiphons") are prayers that come from the Liturgy of the Hours evening prayer during the Octave before Christmas Eve. The Christmas Novena also uses these.
O Antiphons in English (square note notation) following the traditional setting. Listen to them below.
Here is a simplified version of the O Antiphons in English.
Here is the Latin.
Dec 17 - O Sapientia
Dec 18 - O Adonai
Dec 19 - O Radix Jesse
Dec 20 - O Clavis David
Dec 21 - O Oriens
Dec 22 - O Rex Gentium
Dec 23 - O Emmanuel