31. The Middle Ages saw the emergence and development of many spiritual movements and associations of different ecclesiastical and juridical form. Their life and activities had notable consequences for the relationship between Liturgy and popular piety.
+1 for the Dominicans and especially the Franciscans, it would seem:
The new religious orders of evangelical and apostolic life, devoted their efforts to preaching and adopted simpler liturgical forms in comparison to those found in the monasteries. These liturgical forms were often close to the people and to their expressive forms. On the other hand, they also developed and promoted pious exercises that encapsulated their charism, and diffused them among the people.
Lay people continued to live discipleship, even if the liturgy was more and more shut off from them:
The emergence of the Confraternities, with their religious and charitable objectives, and of the lay corporations with their professional interests, gave rise to a certain popular liturgical activity. These often erected chapels for their religious needs, chose Patrons and celebrated their feast days. Not infrequently, they compiled the officia parva and other prayers for the use of their members. These frequently reflected the influence of the Liturgy as well as containing elements drawn from popular piety.
The various schools of spirituality that had arisen during the middle ages became an important reference point for ecclesial life. They inspired existential attitudes and a multiplicity of ways of interpreting life in Christ and in the Holy Spirit. Such interpretations exercised considerable influence on the choice of celebration (e.g. episodes from the Passion of Christ) and were the basis of many pious exercises.
Passion plays feature in our memory of medieval dramas.
Civil society, constituted ideally as a societas Christiana, modeled many of its structures on ecclesiastical usage and measured itself according to the rhythms of liturgical life. An example of this is to be found in the ringing of bells in the evening which called the peasants from the fields and simultaneously signaled the Angelus.
Intentionality or happy accident?
The full document, the Directory on Popular Piety and the Liturgy, is online at the Vatican site.