to reforms called for in the Council of Trent, Pope Pius V promulgated, in the Apostolic Constitution Quo primum of 14 July 1570, an edition of the Roman Missal that was to be in obligatory use throughout the Roman Catholic Church except where there was a traditional liturgical rite that could be proved to be of at least two centuries’ antiquity. The version of the Mass in the 1570s edition became known as the Tridentine Mass. Various relatively minor revision were made in the centuries following, culminating in the 1962 edition promulgated by Pope John XXIII. Pope John XXIII opened the Second Vatican Council that same year, whose participating bishops ultimately called for renewal and reform of the liturgy. The 1969 edition of the Roman Missal was promulgated by Pope Paul VI, issued in response to the council, introduced several major revisions, including simplifying the rituals and permitting translations into local vernacular languages. The version of the Mass in this missal, known colloquially as the Mass of Paul VI, is currently in use throughout the world. Arrangement of churches The Roman Rite of Mass no longer has the pulpitum, or rood screen, a dividing wall characteristic of certain medieval cathedrals in northern Europe, or the iconostasis or curtain that heavily influences the ritual of some other rites. In large churches of the Middle Ages and early Renaissance the area near the main altar, reserved for the clergy, was separated from the nave (the area for the laity) by means of a rood screen extending from the floor to the beam that supported the great cross (the rood) of the church and sometimes topped by a loft or singing gallery. However, by about 1800 the Roman Rite had quite abandoned rood screens, although some fine examples survive. Chant Gregorian chant is the traditional chant of the Roman Rite. Being entirely monophonic, it does not have the dense harmonies of present-day chanting in the Russian and Georgian churches. Except in such pieces as the graduals and alleluias, it does not have melismata as lengthy as those of Coptic Christianity. However, the music of the Roman Rite became very elaborate and lengthy when Western Europe adopted polyphony. While the choir sang one part of the Mass the priest said that part quietly to himself and continued with other parts, or he was directed by the rubrics to sit and wait for the conclusion