The Psalms were probably most often sung antiphonally. They were particularly well suited for that through the verse form, according to which the two parts of a verse are so connected that they express in different words essentially the same thought. This is called parallelism.
This form is not accidental. It encourages us not to allow the prayer to be cut off prematurely, and it invites us to pray together with one another. That which seems to be unnecessary repetition to us, who are inclined to pray too hurriedly, is actually proper immersion and concentration in prayer. It is at the same time the sign that many, indeed all believers, pray with different words yet with one and the same word. Therefore, the verse form in particular summons us to pray the Psalms together.
Quoted from Psalms, The Prayer Book of the Bible by Dietrich Bonhoeffer (Augsburg, 1974), a translation of Das Gebetbuch der Bibel (the 8th ed. published in Germany in 1966). These thoughts are found in the second section, “Who Prays the Psalms?” (pp.23-24)
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