Part III: At the altar

The introit, or entrance antiphon is an old, old prayer. It consists of an antiphon, a psalm verse, the glory be, and the repeated antiphon.
Formerly, an entire psalm was sung between the antiphons, and this was the music that was used for the procession. In the Graduale Simplex, or Simple Gradual, this form of the introit is used. Usually, you will hear it chanted in Gregorian chant, which according to the Second Vatican Council, is still the preferred music of the Roman Rite. There are also many English adaptations. The introit is the first part of what are called the 'minor propers' of the mass. Propers are any part of the mass that changes day to day. They are distinguished between major and minor, so that what is being spoken about is more easily understood.
The major propers are :the opening prayer, the readings, the prayer over the gifts, the preface, and the prayer after communion.
The minor propers are :the introit, gradual or Psalm, offertory antiphon, and communion antiphon.
The introit sets the the theme for the mass, ad eve if our parish doesn't use it, we should still read it ad pray it privately as the priest processes to the altar.
This is the Introit for the 17th Sunday throughout the year: (ordinary time)

(Ps. 67;6-7)
"God is in his Holy temple;
God who makes men of one mind to dwell in a house;
He shall give power and strength to his people.
(Ps. 36:2) Let God arise, let his enemies be scattered, and let those who hate him flee before him.
Glory be to the father, etc.
God is in his Holy temple, etc.

After he genuflects, the priest goes to the altar and kisses it. The altar represents the cross, the first altar, and thus calvary itself. When the priest goes up the steps, we should see Christ, ascending the hill of Calvary. Relics of saints are usually kept sealed up in the altar, and the priest venerates them when he kisses it.
Next, he prepares the incense. We've spoken about incense already. The priest incenses the cross, as a sign of veneration for the crucified Christ, whose sacrifice he will soon offer. He then incenses the altar. Burning incense on the altar was commanded by God under the old covenant, and is done now on the new covenant as a fulfillment of the laws of old. After reverencing the altar, the priest descends the steps.Leaving the altar, the symbol of Christ among us so soon after having reverenced it represents to us the fall of Adam, who so soon after his creation and his dwelling in the presence of God, sinned grievously, and was expelled from Paradise.
Then, he goes to the chair. The chair is set afar from the altar, because, like the devout publican, we stand afar off from the altar of God, being sinners, and like him in the confiteor we pray "O God, be merciful to me a sinner!" (St.Luke 18:13)

"In nomine Patris, et Filii, et Spiritus Sancti"
"In the name of the Father, and of the Son, and of the Holy Spirit"

says the priest, and we all make the sign of the cross. Notice, he says "In the name", not "In the names." These three persons share one name. Whenever we make the sign of the cross, whether we say these words, we mean them, and we confess our belief in the triune God.
We all ratify our belief of this mystery of the faith when we all sing or say "Amen".
The priest turns to us and greets us with the prayer "Dominus vobiscum",
"The lord be with you". Formerly, Christians greeted one another like this, for they are the very words of St.Paul (2 Tim 4:22) We answer, "Et cum spiritu tuo", "And with your spirit". We pray God to be with the soul of the priest as we prepare for the mass. And this is what the priest prays next. He invites us to turn our minds to the sins we have committed, to be sorry for them, and to confess them with contrition in our hearts, that we may be prepared to celebrate the sacred mysteries of the mass.
Together we recite the Confiteor:

"Confiteor Deo omnipotenti"
"I confess to almighty God"

God is the sole source of forgiveness and pardon, though his son Jesus Christ. All pardon we receive, especially that which we receive in the sacrament of penance comes from God.

"Et Vobis Fratres"
"And to you my brethren"

In scripture, we are told to be reconciled with our brothers before we offer our sacrifice. when we recite this, we fulfill Christ's command to do that very same thing.

"Quia peccaviminis, cogitatione, verbo et opere"
"That I have sinned exceedingly in thought, word and deed, in what I have done, and what I have omitted."

Here is mentioned the main types and ways of sinning:
1)Sin in one's thoughts (Such as harboring anger against someone.)
2)Sin in one's words. (Foul language, lying, gossip,etc.)
3)Sin in what one does. ( Sins of commission,Stealing, hurting others, etc.)
4) Sin in what we fail to do. ( Sins of omission,Omitting things like daily prayer, doing penance, helping those in need, cultivating a life with God.)
We sum up when we go to mass and recite this prayer, all our sins. See the wisdom of holy mother church?

"Mea Culpa, mea culpa, mea maxima culpa"
"Through my fault, through my own fault, through my own most grevious fault."

All true sins must have these two qualities:
1) They must be done voluntarily
2) With prior knowledge that the action was sinful.
When we say the mea culpa, we admit that we knew that our actions were sinful, and did them anyway. We admit that we did not follow the inspirations of God through our own fault. We strike ourselves lightly on the chest three time when we say these words, because as the devout John Heigham says "We knock or strike our breasts thereby to make our hard and stony hearts more soft by often beating and knocking." Through frequent confession and repentance,we can sin less and do more to please God.

"Ideo precor beatam Mariam semper Virginem, omnes angelos et sanctos, et vobis fratres, orare pro me adDominum Deum nostrum."
"Therefore, I beg blessed Mary ever Virgin, all the angels and saints, and you my brethren, to pray for me to the Lord our God."

We ask all the saints, principally our blessed mother, to pray for us that we do not fall into these same sins again. The Mother of God, is always named in the Liturgy in the first place — before all the angels and saints, — and her name which, after the name of Jesus, is the sweetest, the most powerful and the most holy, is invariably distinguished by some honorable title which celebrates and expresses her ineffable privileges of grace and glory, chiefly her incomparable virginity and her dignity of the Divine Maternity. For us Mary is the "Mother of Divine grace," "the Mother of mercy," "the Refuge of Sinners," "our dear Lady, our Mediatrix, our Intercessor," "our Life, our Sweetness and our Hope ;" "she obtains for us the clemency of the Father at Christ's throne of grace," and "as the Mother of divine clemency she imparts salvation to her servants," for "God has taken her out of this world, that she may stand before His throne in heaven, an unfailing intercessor in behalf of us poor sinners."5.This shouldn't be just a prayer at mass, but a daily prayer every evening. Which is why in the divine office, we recite it at compline every night. One might notice that in the conteor are contained seven confessions, in fulfillment of the scripture which says "The just man shall fall seven times" (Proverbs 24:16) Even those who have been justified by the precious blood of Christ still suffer the attraction to sin, and even the holiest of saints still sinned.
The priest prays the absolution saying:
Nicholas Girh says of the absolution:

"Then the "almighty" Lord, who "reveals His power most gloriously by sparing the sinner and by exercising mercy," and the "merciful" Lord, "whose property it is always to show mercy and to spare," is again implored to grant us all (nobis) His gracious favor and kind forgiveness, the full remission of sin (indulgentiam), that is, absolution of guilt (absolutionem) and remission of punishment due (remissionem).'' — The accompanying sign of the Cross indicates Christ's atoning sacrificial death, from which flows unto us all forgiveness of sin."

Then, nine times we sing "Kyrie Eleison", "Lord, Have mercy on us." We implore each of the divine persons of the trinity to have mercy on us. John Heigham says of the kyrie:

"These devout petitions are nine times repeated, to put us in mind of nine sorts of sins, wherewith we offend Almighty God. The first three by original, mortal, and venial. The second three by thoughts, words, and deeds. The third three by frailty, ignorance, and malice, and particularly in the last three. Wherefore for our sins of frailty we address our prayer to the Father, saying, Kyrie eleison. For our sins of ignorance to the Son, saying, Christe eleison. And for our sins of malice to the Holy Ghost, saying, Kyrie eleison. "

Then, a triumphant moment. The organist gives a note, and the priest intones alone "Gloria in excelsis Deo" "Glory to God in the highest!"
We sing praise to God, that our sis have been forgiven. we thank him for the benefits of the past week, and in anticipation of the week to come. We adore the Father, our creator, and make petition to Jesus, our paschal sacrifice, and conclude with homage to the entire Trinity. This canticle is called by the church 'The Angelic hymn, because as Eupertus says of it. "This hymn the Church hath taken from the mouth of Angels". It is based on the angelic hymn sung by the angels at the moment of Our Lord's birth, and as the mass is the continuation of the incarnation of Christ, is is meet that we should sing it.
The celebrant, standing before the missal held be the server sings the collect. it is called such, because it collects, or sums up the intentions of our hearts in a prayer to God. It is always an invocation for greater gifts of grace to continue our life as children of God. The collects are ended, as are all the prayers, in the name of Christ, for as John Heigham says:

"First, all the prayers in the Mass are commonly begun in the Name of the Father, and concluded in the Name of the Son ; the Church having conformed herself in this point to the doctrine of our Saviour Himself, saying: Whatsoever you shall ask the Father in My Name, He will give it you."

We sing our "Amen", and sit for the readings.
End for now.