Much of what Agnes sings comes from the Roman Catholic Latin liturgy, primarily the service of the Mass. The term is taken from the words of dismissal of the congregation at the end of the ceremony: “ite missa est.” By the 7th century the Mass had developed into an elaborate rite of chants, prayers and readings. By this time also a distinction was made between those parts of the service whose texts and music were appropriate only to a particular feast (the Proper) and those whose texts and music could be used on any day (the Ordinary). The five portions of the Ordinary are most often set to music, and it is from those selections that Agnes sings. The five sections are known as: Kyrie, Gloria, Credo, Sanctus, and Agnus Dei.

The beginning of the final section, the Agnus Dei, translates as “lamb of God.” One can surmise that Pielmeier is referencing that text in his choice of name for the main character of the play and in the title “Agnes of God.” Agnes is indeed portrayed as an innocent (or lamb), and her alliance with God is an important aspect of the drama.

Other music in the play
“Virgin Mary,” which is sung by both the Mother Superior and Agnes in the middle of the first act is an African-American spiritual.

“Ave Maria,” the other Latin text, besides the portions of the Mass, which Agnes sings is the familiar Roman Catholic prayer “Hail Mary,” part salutation and part petition for deliverance from sin.

“Charlie’s Neat,” sung by Agnes at the very end of the play is an American folk song from the Appalachian Mountains, sometimes described as a “dancing game song.”