In "The Word of God" section for Holy Eucharist, there is an option that "A psalm, hymn, or anthem may follow each Reading." The use of the Psalm, particularly between the Old Testament and Epistles Readings, historically has been referred to as the Gradual. The name comes from the Latin word for "step" because it was generally sung from ambo, pulpit, or the step of the ambo/pulpit.
The Gradual represents the oldest use of the Psalm in liturgy, dating back to the mid-fourth century. While at times other psalms were used in the service, the Gradual was considered necessary and a vital part of the Word the people were hearing. Augustine of Hippo was noted to even use the Gradual Psalm in his preaching. While it is an option, many in the church see the Psalm as a necessary, or at least important, part of the Sunday Lectionary still.
There are times, particularly in the Revised Common Lectionary, when another portion of Scripture replaces, or is given as another option to, the Psalm. Often times these options are one of the Canticles. Psalms were written to be sung, and the Canticles are other such songs that come from various books in the Bible. A great example of a time when a Canticle is given as an option instead of the Psalm for the Gradual is during the 3rd Sunday of Advent with the Song of Mary (also known as the Magnificat).
At times there are other passages of Scripture, generally poetry, that are given as an option for the Gradual in place of the Psalm. An example comes in the readings for Track 1 for the readings of Proper 22 in Year C of the Lectionary. Here we have a passage of Lamentations given as an option for the Gradual, a response, interestingly enough, to the Old Testament reading from the start of Lamentations.
The Gradual is meant as a response to Scripture from Scripture. Through it we further hear what it is God is trying to say to us that particular day as part of our worship together.
Sources Used:
- Cross, F.L. and E.A. Livingstone eds. The Oxford Dictionary of the Christian Church. 3rd edition revised. New York: Oxford University Press, 2005.
- Hatchett, Marion. Commentary on the American Prayer Book. New York: Seabury Press, 1980.
- Mitchell, Leonel. Praying Shapes Believing: A Theological Commentary on The Book of Common Prayer. Harrisburg: Moorehouse Publishing, 1985.