Uniquely in the Liturgical Year the Vigil of the Nativity changes rank after Mattins and from being a simple then becomes a double for Lauds onwards.
Mattins has one nocturn of three lessons. The invitatory is Hodie scietis and the hymn Verbum supernum, the antiphons and psalms are from the ferial psalter (Pss.52, 54, 55, 56, 57, 58, 59, 60, 61, 63, 65 & 67) but the vericles, lessons and responsories are proper. The homily is taken from St. Jerome's commentary on the first chapter of St. Matthew's Gospel. At Lauds proper antiphons, Judaea et Jerusalem nolite timere etc, are sung with the festal psalms. The chapter and antiphon on the Benedictus are proper too.
Prime is festal with the first antiphon from Lauds, as usual, and psalms 53, 118(i) and 118(ii). The Martyrology is sung with extra solemnity today as described on The Saint Lawrence Press blog. The lectio brevis is proper to the Vigil. The antiphons from Lauds are used in sequence at the rest of the Hours.
After None Mass is sung. Today the ministers do not wear folded chasubles but dalmatic and tunicle. There is just one collect. The dismissal, Benedicamus Domino, is sung by the deacon to a most beautiful and ornate tone.
First Vespers of the Nativity are sung in the afternoon. The Office hymn is Christe Redemptor omnium. At Compline (Pss. 4, 30 (vv. 1 - 6)90 & 133) and the hymns of Little Hours from this evening until None on the Vigil of the Epiphany have the Doxology Gloria, tibi Domine, qui natus es de Virgine, Cum Patre et Sancto Spiritu, In sempiterna saecula..