Via Reformation Ireland:
Let us now ask why it is the position of the Reformed churches to limit the songs of worship to the Psalms. In dealing with this we should emphasize that it is not the Reformed position that the use of hymns is wrong. Hymns written by God-fearing people throughout the ages have been a great blessing to God’s people.
The point that we want to make now is this: the Word of God does make plain that the songs to be sung in the worship of Jehovah are to be the songs which the Holy Spirit gave to us, namely the Psalms. If we are to regulate the singing of God’s people by the Word of God, we will make use of those songs which God has provided for us, and which were sung by the church from the very beginning.
You could ask, do not these passages of Scripture teach the opposite? In both texts mention is made of, “Psalms, hymns, and spiritual songs.” In trying to understand what is referred to by this threefold description, we learn that there has been and is much controversy and difference of interpretation. These differences can be broken down into three groups. First, there are those who teach that three different subjects are intended (the view of Jerome and other church fathers): Psalms deal with subjects of an ethical nature; hymns deal with the subject of God’s divine majesty; spiritual songs are concerned with nature and the world. Others suggest that three different forms are intended (the view of Augustine and Hilary): Psalms are to be chanted with music; hymns are for the voice alone; and spiritual songs are to be shouted with short bursts. Finally, there are those who suggest that three different sources are intended (the view of Beza and Grotius): Psalms are Old Testament collections; hymns are collections of various songs such as Song of Mary and Song of Zacharias; and spiritual songs are premeditated compositions prepared for singing.
We consider this threefold description as referring to the Psalms of David. All three (Psalms, hymns, and spiritual songs are designations of the Psalter. We present five considerations. First, if Paul and the Holy Spirit had in mind different kinds of songs other than the Psalms, what songs did He have in mind? It is a historical fact that none existed. The so-called Songs of Mary, etc., did not exist as songs at this period of history; they became songs much later. It is sheer speculation that part of Paul’s epistles were considered odes or songs and that these were intended. Second, the suggestion that Paul was not referring to existing songs, but that he was instructing the church to write them and that this is implied and intended is again doing violence to the scriptures. His burden is to instruct the church to do something now, make use of the songs they already have, use the Psalms, hymns, and spiritual songs as edification and admonition. Third, the word translated “hymn” is used in another passage in the New Testament, Matthew 26:30, where there is no controversy at all but that the hymn that Jesus sang with His disciples at the last Passover was the “hallel” of Psalms 113-118. Fourth, the designation “spiritual songs” is not a reference to some inspired songs in a general way, but very literally Holy Spirit inspired songs. This is the position taken by authorities in Greek such as Thayer, Cremer, and Robertson. What songs did the Holy Spirit give the church? There is only one answer: the Psalms. Finally, the Greek scrolls which were available in the days of Christ and the apostles were known as the Septuagint Bible, the Old Testament Hebrew translated into Greek. This Bible has different headings above each Psalm. (By the way, these headings were not part of the inspired Bible, but were designations added, yet recognized by the early church.) Some Psalms have “Psalms” written above them. In fact, 67 have such a designation. Six have “hymns” written above them, and 35 have “spiritual song” written over them. Some have more than one such designation or combinations.