No one can deny that John Calvin was an ardent lover of the Psalms and believed that they should have the prominent place in the worship and praise of God. However, it is something entirely different to say that John Calvin was an exclusive Psalmist. This fact that he wasn't is proved in a number of ways:
What may be the exact difference between psalms and hymns, or between hymns and songs, it is not easy to determine, though a few remarks on this subject shall be offered on a future occasion.
Psalms, hymns. - He does not restrict the word of Christ to these particular departments, but rather intimates that all our communications should be adapted to edification, that even those which tend to hilarity may have no empty savor. “Leave to unbelievers that foolish delight which they take from ludicrous and frivolous jests and witticisms; and let your communications, not merely those that are grave, but those also that are joyful and exhilarating, contain something profitable. In place of their obscene, or at least barely modest and decent, songs, it becomes you to make use of hymns and songs that sound forth God’s praise.” Farther, under these three terms he includes all kinds of songs. They are commonly distinguished in this way — that a psalm is that, in the singing of which some musical instrument besides the tongue is made use of: a hymn is properly a song of praise, whether it be sung simply with the voice or otherwise; while an ode contains not merely praises, but exhortations and other matters. He would have the songs of Christians, however, to be spiritual, not made up of frivolities and worthless trifles. For this has a connection with his argument.
If these men of a Reformed persuasion believed in exclusive psalmody surely you would expect to find it in the marginal notes of the Geneva Bible. The notes, however, have this to say against Colossians 3:16:
3. The Genevan Psalter of John Calvin's day was not characterised by exclusive psalmody. The Genevan Psalter went through a number of editions. From its commencement Calvin included items of praise from outside the Psalter and even from outside the Scriptures.
The first edition in 1539 contained 17 metrical Psalms plus other 'hymns'. These 'hymns' consisted of a metrical translation of the Ten Commandments; the 'Canticle of Simeon' and the Apostles' Creed for use in singing. The 1543 version, the first published when he was back in Geneva, contained 49 psalms and metrical versions of the Ten Commandments, The Apostles' Creed and the Lord's Prayer. The final version published in 1652 contained all 150 psalms plus the Canticle of Simeon and the Ten Commandments.
1. The terms 'Psalms, Hymns and Spiritual Songs' inEphesians 5:19 & Colossians 3:16 do not refer to the 150 Psalms of the Book of Psalms.
2. Old Testament and New Testament saints did not live by this exclusive psalmist rule.
3. The angels and glorified saints did not sing the psalms.
4. There are possible remnants of hymns/canticles/doxologies quoted in the New Testament.
5. Progressive Revelation argues against Exclusive Psalmody.
6. Exclusive Psalmody leads to different levels of worship.
7. The Exclusive Psalmist's position requires them to reject ever singing the 'very best song' in public worship.
8. If 'inspired praise' is required then an equally valid argument could be made for 'inspired praying' and 'inspired preaching' in public worship.
9. The early New Testament Church did not believe in Exclusive Psalmody.