introit

also In·tro·it (ĭnˈtrōˌĭt, -troitˌ, ĭn-trōˈĭt)

1. A hymn or psalm sung when the ministers enter at the opening of a service, especially in the Anglican Church.
2. Roman Catholic Church The beginning of the Mass, usually consisting of an antiphon, a psalm verse, and the Gloria Patri.