Milan's population, like that of Italy as a whole, is mostly Catholic. It is the seat of the Roman Catholic Archdiocese of Milan. Other religions practised include: Orthodox Churches, Buddhism, Judaism, Islam and Protestantism. Milan has its own historic Catholic rite known as the Ambrosian Rite (Italian: Rito ambrosiano). It varies slightly from the typical Catholic rite (the Roman, used in all other western regions), with some differences in the liturgy and mass celebrations, in the Canons are Easter and Lent, in the colour of liturgical vestments, peculiar use of incense, marriage form, office for the dead, baptism by immersion, and in the calendar (for example, the date for the beginning of lent is celebrated some days after the common date, so the carnival has different date). The season of Advent is of six weeks duration and starts on the Sunday after the feast of Saint Martin (11 November). The Ambrosian rite is also practised in other surrounding locations in Lombardy, parts of Piedmont and in the Swiss canton of Ticino. The sounding of church bells uses a peculiar technique. Another important difference concerns the liturgical music. The Gregorian chant was completely unused in Milan and surrounding areas, because the official one was its own Ambrosian chant, definitively established by the Council of Trent (1545–1563) and earlier than the Gregorian. To preserve this music there has developed the unique schola cantorum, a college, and an Institute called PIAMS (Pontifical Ambrosian Institute of Sacred Music), in partnership with the Pontifical Institute of Sacred Music (PIMS) in Rome
