El Señor reina vestido de Majestad…

This is taken from Psalm 93 (92)
and is generally used for the Christmas season.
One can tell that this is Mozarabic chant,
if not from the arrangement then from the Doxology.

Below are the Latin lyrics and an English translation:

Dominus regnavit, decorem induit. Alleluia
Induit Dominus fortitudinem et praecinxit se. Alleluia.
Gloria et honor Patri et Filio et Spiritui Sancto
in saecula saeculorum. Amen
Dominus regnavit, decorem induit. Alleluia

The Lord hath reigned, He is clothed with beauty. Alleluia
The Lord is clothed with strength, and hath girded Himself. Alleluia
Glory and honor to the Father, and the Son, and the Holy Spirit,
The Lord hath reigned, He is clothed with beauty. Alleluia