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 serving as worship pastor at Ironton Baptist Church. It is set for unison voice, piano, and guitar. The music is set to be sung before the first reading, in between readings, and after the last.