This piece is based on the first half of a melody from the Geneva Psalter, a collection of metrical psalms composed primarily by the 16th-century musician Louis Bourgeois under the guidance of Protestant Reformation theologian John Calvin. The specific psalm tune used here is the one written for Psalm 148. Again, only the first half the of the original melody is used. It should also be noted that the original rhythms have been altered for this arrangement.
Tempo and dynamic markings are included in the piece, but they are offered only as suggestions and not as absolute and immutable guides. I would strongly recommend reading and reflecting upon the psalm for which this tune was originally written (again, Psalm 148) in order to develop one’s own interpretation of the music.