The Cappella Giulia, officially the Reverend Musical Chapel Julia of the Sacrosanct Papal Basilica of Saint Peter in the Vatican, is the choir of St. Peter's Basilica that sings for all solemn functions of the Vatican Chapter,[1] such as Holy Mass, Lauds, and Vespers, when these are not celebrated by the Pope (for functions celebrated by the Pope, the Sistine Chapel Choir sings instead). The choir has played an important role as an interpreter and a proponent of Gregorian chant and sacred polyphony.[2]