The Institutes, Book 2
The Prayer After the Psalm
There is also a practice we have seen in this country: while one person sings the psalm to the end, everyone stands up and sings together in a loud voice, “Glory be to the Father and to the Son and to the Holy Spirit.” We have never heard this anywhere throughout the East. There, when the psalm is finished, all keep silence, and the prayer that follows is offered by the singer. But this hymn in honor of the Trinity is usually used only to close the whole singing of the psalms.