Rob Slane puts forth an argument for what he calls "inclusive psalmody": Why the church needs to sing the Psalms. Here's Slane:
The Psalms, which form the biggest book in the Bible, were clearly meant to be sung, and the Bible gives many exhortations for us to sing them. This is most clearly seen in the Psalms themselves: “Sing to him, sing psalms to him; talk you of all His wondrous works” (Psalm 105:2); “Let us come before His presence with thanksgiving; Let us shout joyfully to him with psalms.” (Psalm 95:2); “Sing unto the Lord with the harp; with the harp, and the voice of a psalm” (Psalm 98:5). . . .
One of the most striking things about the Psalms is that perhaps more than any other book of the Bible, they establish the antithesis, with wickedness on one side and righteousness on the other. This is seen clearly in very first Psalm which divides between on the one hand, the blessed man who “walks not in the counsel of the ungodly” and on the other hand the ungodly man who is “like the chaff which the wind drives away.” The righteous man, it goes on to say, is like “a tree planted by the rivers of water, that brings forth its fruit in its season,” in contrast to “the way of the ungodly (which) shall perish.”