The word “introit” derives from the Latin introitus, meaning “entrance”. Properly speaking, it marks the commencement of the actual Sacrifice. The priest reads the Introit in the Missal even when it is also sung by a choir.
We may call to mind the “official” condemnation of the innocent Lamb accompanied by a blow to His Sacred face.
We pray: “Lord Jesus Christ, who wouldst be brought bound to Annas, as a malefactor, by an armed band of wicked men; give me grace that by no evil spirit, or evil doers, I may be ever drawn to sin, but by Thy goood Spirit led to the fulfilling of Thy divine will. Amen.
As the Mass proceeds we intensify our focus on the Person of Our Lord so that our interior disposition may become something like that of our Blessed Mother’s as she accompanied her Son to Calvary.
In the N.O. the Mass starts with the Entrance Hymn since the preparatory prayers at the foot of the altar were eliminated. From Wikipedia: “Its purpose [ entrance hymn, or chant] is to open the celebration, foster the unity of those who have been gathered, turn their thoughts to the mystery of the celebration, and accompany the procession. If there is no singing at the Entrance, the antiphon in the Missal is recited either by the faithful, or by some of them, or by a lector; otherwise, it is recited by the priest himself, who may even adapt it as an introductory explanation.”