My Latin, while good, I'm much too lazy to use it at this hour, so I'm going to put it in English...I'm sure someone can forward all this to the Vatican later. I've cut all the useless language out, and got straight to the point, no need to BS.
The official GIRM is here
1) The Holy Sacrifice of the Mass has four ends: 1) Adoration of the Holy Trinity 2) Contrition for our sins 3) Thanksgiving for Gods blessings and 4) Supplication or Intercession for our needs. It is a mortal sin against justice to abuse the Holy Sacrifice of the Mass in any way. The Holy Sacrifice of the Mass must be offered in full fidelity to the rubrics of the Missal, and neither a priest, Bishop or Pope has the authority to change the rubrics on his own accord.
2) What follows are not suggestions but mandates to the theological virtue of justice and the extension of right worship and religion.
II Music for the Holy Sacrifice of the Mass
3) Gregorian chant is to be used for all Masses. This may be done in the vernacular or Latin.
4) Hymns may be sung at the following points: Before the Introit, After the Offertory Chant, Before the Homily, After the Communion chant and accompanying verses, following the Dismissal and Last Gospel
5) Sources for Hymns may be taken from any Catholic or Orthodox source.
6) Secular songs are forbidden from the Liturgy.
7) Ab libbing from the texts that are prescribed is explicitly forbidden and a mortal sin against justice and the virtue of religion.
8) All texts from the Missal are to be sung according the the prescribed melodies in the Missal.
III The structure of churches, oratories and Cathedrals.
9) The Tabernacle must be in the center for every parish and oratory. For the Cathedral parish, the Tabernacle is to be located in a side chapel or a chapel near the altar of sacrifice, for the Bishop is High Priest for his diocese.
10) The altar of sacrifice may be free standing or attached. There must be room for Ad Orientem celebrations.
11) Altar railings must be in every parish to distinguish the sanctuary from the nave.
12) Architecture that does not communicate the Catholic Faith must be avoided...Modernism is a heresy which is condemned, and can't take form in the architecture of the local church.
13) The priest's chair must not face the congregation and off towards the epistle side of the altar.
14) The throne of the Bishop should be on the Gospel side of the altar....or for churches built in the basilica style behind the altar in the traditional manner.
15) The altar must be covered with three cloths as is traditional.
16) The traditional veiling of the Tabernacle is encouraged to be retained.
17) Statues and Icons are to be used liberally through the church.
18) Confessionals are to be gated as to maintain anonymity.
19) Holy Water fonts are to be filled at all times except during the Holy Triduum.
20) The tradition of side altars should be maintained.
21) Choir lofts are to be built in the back.
22) Chairs in choir must face the traditional direction.
Anything I've missed so far? I'm open to suggestions....