Viderunt omnes

"Viderunt omnes" is a Gregorian chant based on Psalm XCVII (98), sung as the gradual[1] at the Masses of Christmas Day and historically on its octave, the Feast of the Circumcision. Two of the many settings of the text are famous as being among the earliest pieces of polyphony by known composers, Léonin and Pérotin of the Notre Dame school. Their music, known as organum, adds florid counterpoint to the Gregorian melody of the intonation and verse, portions normally sung by the cantors, the remainder of the chant being sung unchanged by the choir.


The text, from Ps. 98:3cd, 4, 2, describes God's oversight of the Earth, an especially symbolic message given the musical unity that the composition came to represent.