My favorite Old Testament book is the Psalms, which I think it is the favorite of a lot of Christians. One of the reasons I love the Psalms is the honest prayers of those who are writing these songs. Another reason is how God is exalted in every Psalm where the readers get his/her eyes to things above.
The Psalms are considered the original hymnbook to many Christians. There have been a number of songs written based on the Psalms and whole albums as well. A lot of these songs based on the Psalms are indeed more worthy of being called a worship song compared some modern songs that are sung in the church today, which leads to the question, should the church being singing only the Psalms?
There is a growing number of believers that think this is the better way to worship the Lord because all the songs would be based on the Word of God, which is commendable. However, we do not see any evidence in the Bible that we are to sing only Psalms. In the Bible, we see these two passages that parallel one another:
Therefore do not be foolish, but understand what the will of the Lord is. And do not get drunk with wine, for that is debauchery, but be filled with the Spirit, addressing one another in psalms and hymns and spiritual songs, singing and making melody to the Lord with your heart, giving thanks always and for everything to God the Father in the name of our Lord Jesus Christ, submitting to one another out of reverence for Christ (Ephesians 5:17-19).
Let the word of Christ dwell in you richly, teaching and admonishing one another in all wisdom, singing psalms and hymns and spiritual songs, with thankfulness in your hearts to God (Colossians 3:16).
When we come together in worship, we are sing music that honors God and lift up praise to Him. R. Kent Hughes wrote:
(W)hen the church comes together there is verbal, musical communication—both horizontal and vertical...The Roman governor Pliny, in his famous letter to the Emperor Trajan in A.D. 112, tells how the Christians in his province had the custom of meeting on a fixed day before dawn and “reciting a hymn antiphonally to Christ as God.” Tertullian, writing from North Africa toward the end of the same century, describes a Christian feast at which “Each is invited to sing to God in the presence of others from what he knows of the holy scripture or from his own heart.” Putting all this together we get the idea: some sang “psalms” from the Old Testament Psalter, some sang new Christian “hymns,” perhaps like those in Revelation 4, 5, and some sang “spiritual songs”—unpremeditated praise from the heart. Imagine how beautiful and soul-satisfying these meetings must have been under the orchestration of the Holy Spirit.
I don't think there is nothing wrong with singing the Psalms in our worship services, but we must be careful that it does not become ritualistic or even legalistic. The same is true for hymns and spiritual songs. Jesus and the disciples sang a hymn as they concluded the Last Supper (Matthew 26:30). There are a great number of hymns and worship songs for Christians to sing.
Granted there are a number of them that we must stay clear from. If a collection of songs come from a church or an individual known for heresy, then we should stay clear from those songs entering in our congregations. Just because a song is played on Christian radio, it does not qualify it as a worship song. What should qualify it is if it is in line with the Bible. Jesus says those who worship God are those who worship in spirit and in truth. To worship in truth means to worship God based in His revealed word to us. There are many things God has shown us about Himself in the Psalms, but there are other places in scripture He has done so as well.