Simply put, the Psalms were the hymns of the Israelites. "On the basis of internal evidence, some of the psalms seem to indicate that they were used for public worship, some for private devotion, and some for the celebration of specific events" (Reynolds & Price, A Survey of Christian Hymnody, 1). There is also substantial evidence showing how the Psalms were used in worship by the Church, both in the New Testament and the Ecclesiastical era.
I wrote this arrangement of Psalm 54 when I was