General Instruction of the Roman Missal: Chapter V, The Arrangement and Furnishing of Churches
III. The Arrangement of the Church
The Places for the Faithful
311Places should be arranged with appropriate care for the faithful so that they are able to participate in the sacred celebrations visually and spiritually, in the proper manner. It is expedient for benches or seats usually to be provided for their use. The custom of reserving seats for private persons, however, is reprehensible.[122] Moreover, benches or chairs should be arranged, especially in newly built churches, in such a way that the people can easily take up the postures required for the different parts of the celebration and can easily come forward to receive Holy Communion.
Care should be taken that the faithful be able not only to see the priest, the deacon, and the lectors but also, with the aid of modern technical means, to hear them without difficulty.
The Place for the Choir and the Musical Instruments
312The choir should be positioned with respect to the design of each church so as to make clearly evident its character as a part of the gathered community of the faithful fulfilling a specific function. The location should also assist the choir to exercise its function more easily and conveniently allow each choir member full, sacramental participation in the Mass.[123]
313The organ and other lawfully approved musical instruments are to be placed in an appropriate place so that they can sustain the singing of both the choir and the congregation and be heard with ease by all if they are played alone. It is appropriate that, before being put into liturgical use, the organ be blessed according to the rite described in the Roman Ritual.[124]
In Advent the organ and other musical instruments should be used with a moderation that is consistent with the season’s character and does not anticipate the full joy of the Nativity of the Lord.
In Lent the playing of the organ and musical instruments is allowed only to support the singing. Exceptions are Laetare Sunday (Fourth Sunday of Lent), solemnities, and feasts.
The Place for the Reservation of the Most Holy Eucharist
314In accordance with the structure of each church and legitimate local customs, the Most Blessed Sacrament should be reserved in a tabernacle in a part of the church that is truly noble, prominent, readily visible, beautifully decorated, and suitable for prayer.[125]
The one tabernacle should be immovable, be made of solid and inviolable material that is not transparent, and be locked in such a way that the danger of profanation is prevented to the greatest extent possible.[126] Moreover, it is appropriate that, before it is put into liturgical use, it be blessed according to the rite described in the Roman Ritual.[127]
315It is more in keeping with the meaning of the sign that the tabernacle in which the Most Holy Eucharist is reserved not be on an altar on which Mass is celebrated.[128]
Consequently, it is preferable that the tabernacle be located, according to the judgment of the diocesan Bishop,
Either in the sanctuary, apart from the altar of celebration, in a form and place more appropriate, not excluding on an old altar no longer used for celebration (cf. no. 303);
Or even in some chapel suitable for the faithful’s private adoration and prayer[129] and organically connected to the church and readily visible to the Christian faithful.
316In accordance with traditional custom, near the tabernacle a special lamp, fueled by oil or wax, should be kept alight to indicate and honor the presence of Christ.[130]
317In no way should all the other things prescribed by law concerning the reservation of the Most Holy Eucharist be forgotten.[131]
Sacred Images
318In the earthly Liturgy, the Church participates, by a foretaste, in that heavenly Liturgy which is celebrated in the holy city of Jerusalem toward which she journeys as a pilgrim, and where Christ is sitting at the right hand of God; and by venerating the memory of the Saints, she hopes one day to have some part and fellowship with them.[132]
Thus, images of the Lord, the Blessed Virgin Mary, and the Saints, in accordance with the Church’s most ancient tradition, should be displayed for veneration by the faithful in sacred buildings[133] and should be arranged so as to usher the faithful toward the mysteries of faith celebrated there. For this reason, care should be taken that their number not be increased indiscriminately, and that they be arranged in proper order so as not to distract the faithful’s attention from the celebration itself.[134] There should usually be only one image of any given Saint. Generally speaking, in the ornamentation and arrangement of a church as far as images are concerned, provision should be made for the devotion of the entire community as well as for the beauty and dignity of the images.