Haec dies (Psalm 118:24,1) – Perotin
24 This is the day that the Lord has made; let us rejoice and be glad in it.
1 O give thanks unto the Lord; for he is good: because his mercy endureth for ever.
Haec est dies quam fecit Dominus; exsultemus, et laetemur in ea. Confitemini Domino, quoniam bonus, quoniam in saeculum misericordia ejus.
Haec est, composed by Pérotin (fl. c. 1200)
^Performed by Cantica of the Czech Republic