27. Mention must be made of the pontificate of the great pastor and liturgist Pope St. Gregory VII (590-604), since it is regarded as an exemplary reference point for any fruitful relationship between the Liturgy and popular piety. Through the organization of processions, stations and rogations, Gregory the Great undertook a major liturgical reform which sought to offer the Roman people structures which resonated with popular sensibilities while, at the same time, remaining securely based on the celebration of the divine mysteries. He gave wise directives to ensure that the conversion of new nations did not happen without regard for their own cultural traditions. Indeed, the Liturgy itself could be enriched by new legitimate cultic expressions and the noble expressions of artistic genius harmonized with more humble popular sensibilities. He established a sense of unity in Christian worship by anchoring it firmly in the celebration of Easter, even if other elements of the one mystery of Salvation (Christmas, Epiphany, and Ascension) were also celebrated and the memorials of the Saints expanded.
It’s interesting to contrast the openness of the early Church to new expressions in comparison to the stranglehold the Tridentine stasis had on much of Roman Catholicism during a time when it may have been sorely needed.
The full document, the Directory on Popular Piety and the Liturgy, is online at the Vatican site.