The Ceremonial of Bishops sets the context in no. 297: “With this Mass, celebrated in the evening of the Thursday in Holy Week, the Church begins the sacred Easter Triduum and devotes herself to the remembrance of the Last Supper. At the super on the night he was betrayed, the Lord Jesus, loving those who were his own in the world even to the end, offered his Body and Blood to the Father under the appearance of bread and wine, gave them to the apostles to eat and drink, then enjoined the apostles and their successors in the priesthood to offer them in turn. This Mass is, first of all, the memorial of the institution of the eucharist, that is, of the Memorial of the Lord’s Passover, by which under sacramental signs he perpetuated among us the sacrifice of the New Law. The Mass of the Lord’s Supper is also the memorial of the institution of the priesthood, by which Christ’s mission and sacrifice are perpetuated in the world. In addition, this Mass is the memorial of that love by which the Lord loved us even to death…”
The rubrics, by way of exception, allow for the local Ordinary to permit another Mass in churches and oratories to be celebrated in the evening, and, in the case of genuine necessity, even in the morning. Such Masses are provided for those who are in no way able to participate in the evening Mass and not for the advantage of individuals or (newly added) special small groups (Missale Romanum, “Rubrics for The Evening Mass” (EM, no.3).
The rubrics then make a mention of the liturgical decoration. “The altar may be decorated with flowers with a moderation that reflects the character of the day” (EM, no.5).
The Church bells are rung during the singing of the Gloria and then remain silent unless the “diocesan Bishop, as circumstances suggest, decides otherwise” (EM, no.7). The decision about this matter no longer involves the conference of bishops. A further musical specification is provided: “the organ and other musical instruments may be used only to support the singing” (EM, no. 7)
The rubric following the washing of the feet is more descriptive than the presently existing one: “After the washing of the feet, the priest washes and dries his hands, puts the chasuble back on, and returns to the chair, and from there he directs the General Intercessions. The Creed is not said” (EM, no. 13).
In a new rubric it is noted that “at an appropriate time during Communion, the priest may entrust the Eucharist from the table of the altar to the deacons or acolytes or other extraordinary ministers, so that afterwards it may be brought to the sick who must communicate at home” (EM, no. 33). This may require that parishes do some preliminary planning for this to successfully happen.
It is explicitly stated that the prayer after Communion is said by the priest “standing at the chair” (EM, no. 35).
The order of procession is more carefully described for the transfer of the Blessed Sacrament to the place of reposition. Newly added is the description : “A lay minister with a cross between two others with lit candles follow. Before the priest carrying the Blessed Sacrament comes the censer bearer with a smoking censer” (EM, no. 38).
The directions for what the priest should do once he reaches the place of reposition have been supplemented. “…the priest, with the help of the deacon if necessary, places the ciborium in the tabernacle, the door of which remains open” (EM, no.39). He then incenses the Blessed Sacrament while Tantum Ergo Sacramentum or another Eucharistic song is sung. Then the “deacon or the priest himself places the Blessed Sacrament in the tabernacle and closes the door” (EM, no. 39).
The previous Missale Romanum seemed to indicate that the stripping of the altar followed immediately whereas the new Missale Romanum notes that “at an appropriate time” the altar is stripped (EM. no. 41).
The faithful are “invited” in the new Missale Romanum to spend time in adoration. It was formerly indicated that the faithful “should be encouraged” (EM, no. 43).
A totally new rubric is found at the end of Holy Thursday. “If in the same church the celebration of the Lord’s Passion on the following Friday does not take place, the Mass is concluded in the usual way and the Blessed Sacrament is placed in the tabernacle (EM, no. 44).