Last week I published links to two items, one by Michael Bird, (less serious) and the other (more serious) by David Robertson on the merit of the Free Church of Scotland changing its long standing custom of only singing material (mostly Psalms) that comes from the Bible.
R. Scott Clark has a post (and lengthy comments thread) in which he asserts, maintains and defends the principle that congregational singing in church should be the words of the Bible.
Though Clark often points those with different points of view to his book Recovering The Reformed Confession (fairly enough), the thread deals with the issue in enough depth for you to get a fair idea of the debate.
I think Clark over applies the regulative principle, selectively appeals to Scripture and early church practice and takes a position regarding the congregation corporately only being able to respond to God with Scripture that does not apply in any other aspect of worship.
Read: Deformation Or Reformation?