In the revision and renewal of the Liturgy of the Hours that was completed in the early 1970s, one of the important and interesting changes was the addition of “psalm-prayers”, collects that are inserted after each psalm and canticle. As §112 of the General Instruction of the Liturgy of the Hours puts it:
Orationes super psalmos, quae recitantes adiuvent in eorum interpretatione praecipue christiana, in Supplemento libri Liturgiae Horarum pro singulis psalmis proponuntur et possunt ad libitum adhiberi ad normam veteris traditionis, ita scilicet ut, absoluto psalmo et aliquo silentii spatio observato, oratio psallentium affectus colligat et concludat.
“Prayers on the psalms, to help those who recite the psalms to interpret them in a particularly Christian sense, are offered for each psalm in the Supplement to the Liturgy of the Hours. They can, if wished, be added to the Office, following an ancient tradition – that is, the psalm having been completed and a certain period of silence having been observed, to bring together the thoughts and feelings of those who have recited the psalm, and to bring them to a conclusion.”
That section does not say anything about exactly when the psalm-prayers should be said (if people choose to use them). Some American books place the psalm-prayers before the final antiphon. This is wrong. The psalm-prayer should go after the final antiphon and an optional period of silence. Here is §202 of the General Instruction:
The purpose of this silence is to allow the voice of the Holy Spirit to be heard more fully in our hearts, and to unite our personal prayer more closely with the word of God and the public voice of the Church. […] Periods of silence may be inserted in different ways: after the psalm, once its antiphon has been repeated… and especially if there is a Psalm-prayer after the silence…
Accordingly Universalis places the psalm-prayers after the final antiphon.