Psalm prayers are used in Matins and Vespers after the singing or chanting of a psalm. In Christian Worship, our hymnal, they are used only in Evening Prayer (=Vespers), but it seems that historically they were always used with the psalms (as far as I can tell, anyway.) The psalm prayer gathers together the thoughts of the psalm and recaps them for the worshipper; they focus the worshipper’s thoughts and meditation and provide an opportunity to reflect on what the psalm says for us. Many of them are beautiful and deserving of reflection in their own right. This psalm prayer, for use with Psalm 74, is a good example of the type. I prayed this as part of Matins this morning.
O God, creator of all the elements, King everlasting before the worlds, remember Thy flock which Thou hast redeemed by the shedding of Thine own Blood, and graciously hear the voices of all them that seek Thee, O Savior of the world; who livest and reignest with the Father and the Holy Ghost, ever one God, world without end. Amen. (Brotherhood Prayer Book, 2nd ed., p.240)
As well as being beautiful and majestic in their language, these psalm prayers have the added benefit of being crystal-clear doctrinally. Through long use in the church, these prayers have been honed and refined into confessions of the faith that Scripture teaches, without mixing anything that should be kept separate or inventing new terms or categories. They teach as well as pray. Newly written prayers (and orders of service, while we’re on the topic) don’t have that distilling and correcting influence of long use in their favor…yet another reason not abandon the church’s traditional ways of praying and worshipping.