While crowding against the railings of St. Peter’s Square during a Dec. 31 blessing of the Vatican’s Nativity scene, students of Mary Immaculate Catholic School began to take up the tune of “Hark! The Herald Angels Sing.” As they raised the hymn, the students were greatly surprised to discover the addition of a new voice: that of Pope Leo XIV, who had paused in his rounds to join in the festive song.