“2. The Covenanter Church believes that it is sinful to sing uninspired hymns in the worship of God. The Presbyterian, Methodist and many other denominations do not so believe. We are convinced that we can give a valid Scriptural proof for our position on this matter. To us it is not a matter of indifference, but a very important matter indeed. How Almighty God is to be worshipped is no trifle to be decided according to human pleasure and preference. But the advocate of open communion asks, in effect, that the position of the Presbyterian and Methodist Churches be made the rule that shall govern the practice of the Covenanter Church concerning admission to the Lord’s Supper.”
J.G. Vos discussing admittance to the Lord’s table.
The whole work can be found here
Exclusive Psalmody 