95 Some in fact disapprove altogether of those Masses which are offered privately and without any congregation, on the ground that they are a departure from the ancient way of offering the sacrifice; moreover, there are some who assert that priests cannot offer Mass at different altars at the same time, because, by doing so, they separate the community of the faithful and imperil its unity; while some go so far as to hold that the people must confirm and ratify the sacrifice if it is to have its proper force and value.
Source: Mediator Dei (Vatican.va)