WARNING: DO NOT SING THIS UNTIL LATER IN ADVENT. YOU CAN LISTEN BUT DO NOT SING.
Wow. Really beautiful. Even better in Latin.
On the subject of beautiful music and chant, the Benedictines of Mary, Queen of Apostles, a Priory in Missouri, USA have produced a wonderful new Advent CD that would be well worth buying as a gift for someone for Christmas. Click here to buy a copy. Here is a promotional video below for the Benedictines of Mary.