John Cotton has a chapter devoted to the question of whether carnal men may sing psalms (a cappella) along with godly Christians in his treatise on the singing of psalms (he answers in the affirmative). You can purchase it here or read it online here.

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Andrew Myers
Husband of Jessica, Father of Jackson, Katie and Samuel
Member, Presbyterian Reformed Church of Northern Virginia
Warrenton, VA USA
Editor, The Matthew Poole Project

"Let your Morning Thoughts, and your last Evening Thoughts, be what shall become of you to all Eternity." -- Matthew Poole