If another rite immediately precedes Mass, such as the Palm Sunday procession or the various ceremonies that precede Mass at the Easter Vigil, Mass begins with the collect there is no Entrance at that point and so no Entrance chant. 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 mayД®ven adapt it as an introductory explanation. Its purpose 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. Since the 1970 revision of the Roman Missal, the Entrance chant begins as the priest enters. It also has him make the sign of the cross, when reading it, a relic of the time when Mass began with it. The Tridentine Mass has the priest read the Introit in the Missal even when it is also sung by the choir. Until 1908, even in sung Mass the choir began the Introit only after the priest had begun those prayers, but Pope Pius X restored the old arrangement whereby the Introit accompanied the entrance procession of the priest with the ministers. In Low Mass, the priest reads it only after the Prayers at the Foot of the Altar. In the Tridentine Mass the Introit is no longer the first text used in the Mass. The words of the antiphons are related to the theme of the feastday or celebration and most frequently have something in common with the liturgical readings of the Mass. In some rare cases the antiphon is not from Scripture: 'Salve, sancta parens', from the Christian poet Sedulius, who was imitating a line from book V of Virgil's Aeneid, is the antiphon used in the Tridentine form of the Roman Rite for common Masses of the Blessed Virgin Mary the 1970 revision kept a Mass formula of the Blessed Virgin with that antiphon, but provided several alternatives. The antiphons of most Introits are taken from Psalms, though many come from other parts of Scripture. In contemporary Catholic usage, the introit corresponds to the Entrance Antiphon and is sung or recited audibly throughout by the faithful. The 1970 revision of the Roman Missal explicitly envisages singing the entire psalm associated with the antiphon, but does not make it obligatory. In time only the opening verse of the psalm was kept, together with the Gloria Patri, preceded and followed by the antiphon, the form of the Introit in Tridentine Mass Roman Missals, which explicitly indicate this manner of singing the Introit. If singing of the psalm was not completed by the time the Entrance procession arrived at the altar, the singers moved directly to the Gloria Patri and the final repetition of the antiphon. Pope Gregory I (590вЂ“604), after whom Gregorian chant is named, composed several antiphons for singing with the Entrance psalm. The change to this manner of singing the psalm has been attributed to Pope Celestine I (422вЂ“432). While the psalm was at first sung responsorially, with an antiphon repeated by all at intervals, while a solo singer chanted the words of the psalm, it was soon sung directly by two groups of singers alternating with each other, and with the antiphon sung only at the beginning and the end, as is the usual way of chanting the psalms in the Liturgy of the Hours. Originally, the entrance of the priest who was to celebrate Mass was accompanied by the singing of a whole psalm, with Gloria Patri (doxology). In the Mozarabic, Carthusian, Dominican, and Carmelite Rites, it is called the 'officium'. In Ambrosian chant and Beneventan chant, the counterpart of the Introit is called the ingressa. In pre-1970 editions of the Roman Missal, the word Introitus was used, distinguished from the normal meaning of the word (entrance) by being capitalized. In the Roman Rite of the Catholic Church it is known as the antiphona ad introitum (Entrance antiphon), as in the text for each day's Mass, or as the cantus ad introitum (Entrance chant) as in the General Instruction of the Roman Missal, 47 and the First Roman Ordo (sixth to seventh century). It is part of the Proper of the liturgy: that is, the part that changes over the liturgical year. In its most complete version, it consists of an antiphon, psalm verse and Gloria Patri, which are spoken or sung at the beginning of the celebration. The Introit (from Latin: introitus, 'entrance') is part of the opening of the liturgical celebration of the Eucharist for many Christian denominations.

Gregorian chant history