It’s a long-standing tradition in Presbyterian churches to conclude the responsive psalm by singing or speaking a doxology called the Gloria Patri (a doxology is a brief expression of praise to God). The Gloria is an ancient Latin doxology: Gloria Patri, et Filio, et Spiritui Sancto; sicut erat in principio, et nunc, et semper, et in saecula saeculorum. Amen. The standard modern translation in English is Glory to the Father, and to the Son, and to the Holy Spirit; as it was in the beginning, is now, and will be for ever. Amen.
The Gloria Patri serves as a kind of “Christianizing formula” at the end of the psalm, emphasizing that the God spoken of in the psalm is the same God whom we worship as Father, Son, and Holy Spirit. At one time, the Gloria was commonly sung to an “Anglican chant” tune in Presbyterian churches, and the 1972 edition of the hymnbook provided three such tunes. The current hymnbook has two settings of the Gloria, one at #594 (the old translation) and the other at #684 (the modern translation), neither of which are Anglican chants.