100th Anniversity of Pope Saint Pius X's Launch of the Liturgy Reform Movement Tra le sollecitudini called for revival of Gregorian Chant One hundred years ago, on the feast of Saint Cecilia, Pope Saint Pius X issued directives on sacred music that gave encouragement and direction to the reform of the Liturgy, in addressing the nature of sacred music appropriate for use at Mass. In this directive, known by its Italian title, Tra le sollecitudini ("among the concerns"), the pope uses for the first time the expression actuosa participatio (active or actual participation) of the people in the celebration of...