|Not quite the quire of Westminster Abbey|
source: New Liturgical Movement
The most obvious changes can be viewed from the lens of architecture. Upon walking into a post-Tridentine church one easily sees the high altar, elevated against the reredros and crowned in the center with the tabernacle. The sacred space is partitioned by a Communion railing [sic], a hint that the sanctuary is something to be viewed and not touched. The ceiling ascends heavenward and without obstruction, an open and breathing arrangement. Additional altars to saints flank the main altar, although their use for Mass is more infrequent than in past times; these altars proclaim tales of heresy, fidelity, damnation, and the glory of the saints; each altar is as much a sermon as it is a shrine. Scattered Confessionals awkwardly stand out of any open space in the nave or aisles of the church, invitations for ambulating sinners to reconcile themselves at a moment's notice. Most obviously, and loathsomely, pews litter the nave itself, confining anyone who desires to witness the Holy Sacrifice to his own static place, a sight-seer and viewer of the Mass and devotions rather than a full participant in them.
Within this casual characterization of a post-Tridentine church rests a thousand assumptions concerning the change in liturgical praxis, although rarely text, that followed the pontificate of St. Pius V. Above all, the post-Tridentine liturgy emphasized witness to the liturgy and Incarnation rather than a personal and communal participation in Christ's Passion which characterized the preceding medieval cathedral rites. Medieval churches, narrow and high, impossible to see straight in unless one was staring down the nave at the Holy Rood, always directed the attention of the faithful to the Cross and then upward; everything else was shrouded in mystery, things one could see and to an extant understand, but not know in entirety. After Trent the prevailing designs suggested a liturgy which could be beheld and known, for it took place in plain sight.
Devotion in this piety shifted away from the Divine Office and more toward new liturgical acts of piety which underscored the arrant nature of the new liturgy. Now, when the priest held up the Sacred Species during the Canon saw the Incarnated Christ in open space. Unlike previous generations, peering through screens at the elevation once a Mass, new generations would extend the elevation of the Sacred Host by means of a new ceremony called Benediction. They sang hymns and offered incense before directly displaying the Sacred Host for a few moments in blessing, a short time to be sure, but more time than was afforded during the Mass. The song of the day was no longer Ave verum corpus, but Tantum ergo Sacramentum.
These new forms of devotion met the mood of the day, still largely communitarian in towns, but more amotized in cities, where Catholicism went from being the religion of the people to being the religion of the majority of people. Personal encounters with grace, be it Confession or Benediction or a quick Mass, replaced the public processions and liturgical anamnesis which would derisively be rebranded as theater in our times.
Mass itself underwent a simplification in its ceremonial observance. As sounds became more complex and polyphony superseded chant as the normative style, people came to see music more as ornamental than as essential. Following the reduced ceremonies of the Roman Curia's Missal published by Saint Pius, servers and ministers followed the prescriptions as to what needed to be done to complete the Sacrifice. Said Mass replaced sung Mass, even without deacon and subdeacon, as normative. Still, a desire for the Mass to be sung and celebrated with as much effort as possible prevailed in some places and a sung version of low Mass evolved into the Missa cantata, styled more as a "high" Mass without the other ministers.
Once of the less obvious liturgical changes since Trent, which was not a variation of something directed in the Missal, was the addition of rose as a liturgical color. The medieval and Pian Missals directed violet for Gaudete and Laetare Sundays. The true differentiation between these Sundays and the other Sundays of Advent and Lent are the use of the dalmatic and tunicle instead of folded chasubles, which would also permit the organ to be used to elevate the music from sober chant into polysonic joy. Rose accomplished a similarly end, providing a break in the exercises of the seasons, to a culture bent towards a simpler liturgy. Rose eventually gave birth to a vast array of colors deemed proper for the Mass and even replaced the seasonal violet in the cardinatial choir dress on those Sundays.
Liturgy as it existed in the years after Trent has been examined and criticized extensively on this blog for its reduction of the Latin liturgy to bare essentials which neglected large pieces of the Church's patrimony. In context, these reductions also reflected creeping individualism and a less communal culture from which sprang the medieval Mass. And yet the post-Tridentine Church was not without its own development in art, architecture, liturgy, and devotion. One wonders what a genuine reform to the liturgy would look like in our even more isolationist age.