Before we begin to examine the possibilities in actual practice today, we shall summarize, as clearly as we can, what has been said thus far. What are the Proprium or “Proper” chants of the Roman liturgy? They are sacred texts chosen chiefly from the Bible, sung in a liturgical context (i.e. performed as appropriate to the individual moments or actions of the Mass) on the various days of the (Church) year.
Why were changes introduced after the Council? In the case of the Proprium chants, we may surmise that aims like the following were involved:
a) to draw the entire congregation into the singing;
b) to offer ordinary or conventional texts in place of the biblical verses which require a higher degree of liturgical formation and knowledge from the faithful, and yet they are also
c) in the vulgar tongue, on simple tunes;
d) and to abrogate or dissolve the fixed position of a given chant, i.e. its connection with a given day and a given part of the liturgy;
e) so as to permit the use of a repertory pleasing to various ethnic, social or age groups.
The reader himself can judge which of these objectives harmonizes with heritage of the Roman liturgy or with the conciliar Liturgical Constitution. In any case, the goals listed above are very useful in indicating the difficulties faced by anyone who wishes to propose a solution.
Laszlo Dobszay, The Bugnini-Liturgy and the Reform of the Reform (2003)