Roberts (1609–1675) was an influential English puritan who wrote a very large introduction to the Bible, from which this work is taken.
Roberts gives 8 very helpful directions on how to sing the psalms with the most spiritual profit. Print out these directions as a pamphlet to help fellow saints be encouraged in the Lord.
This 12 page document is from pp. 128-131 of his larger
The Key of the Bible: Unlocking the Richest Treasury of the Holy Scriptures. This is an updated and easier to read edition than the original.