This is a recording of the Cherubic Hymn which is sung at every Divine Liturgy just before the Great Entrance. In the video the words are very long and drawn out, so it's sometimes hard to understand what is being said. Here are the words for those who are not familiar with this hymn:
Let us who mystically represent the Cherubim
And sing to the Life-giving Trinity the Thrice Holy Hymn
Now lay aside all earthly cares
That we may receive the King of all
Who comes invisibly up-borne by the angelic hosts.
Alelluia! Alelluia! Alelluia!