Which changes are harmless and which are liturgical abuse?
I think that this is an easy question to answer. Priests and other self-proclaimed masters of the Sacred Liturgy, on the other hand, would probably disagree.
The Constitution on the Sacred Liturgy, Sacrosanctum Concilium, makes it very clear on who can change the Holy Mass. Consider:
- Regulation of the sacred liturgy depends solely on the authority of the Church, that is, on the Apostolic See and, as laws may determine, on the bishop.
- In virtue of power conceded by the law, the regulation of the liturgy within certain defined limits belongs also to various kinds of competent territorial bodies of bishops legitimately established.
- Therefore no other person, even if he be a priest, may add, remove, or change anything in the liturgy on his own authority.
Sacrosanctum Concilium, Section 22
So that is the food chain: Rome is at the top, competent territorial bodies of bishops (in the USA that would be the USCCB) are next, but only with Rome’s approval, and finally the bishop, but only insofar as he is permitted by law.
Presently, for example, the US bishops are working with Rome on a new English translation for the Mass. The US bishops cannot implement this new translation, however, until Rome approves it.
Even a bishop is granted (very) limited power to determine what is liturgically proper in his diocese. A bishop can, for example, forbid reception of communion in the hand, but cannot forbid reception on the tongue. A bishop can determine whether congregations in his diocese shall stand or kneel after the Agnus Dei, but he cannot make such a determination during the Eucharistic Prayer (all must kneel).
Understand also, that there are legitimate options that a priest does have. There are three acceptable greetings, three forms of the penitential rite (plus the sprinkling of water, when appropriate), four regular Eucharistic Prayers (plus those for reconciliation and those for Masses with children), and four different memorial acclamations.
If you want to find out more about what is liturgically proper and what is not, read the General Instruction of the Roman Missal (available for download in pdf format from the USCCB website).
usccb.org/liturgy/current/revmissalisromanien.shtml
MT