While Gordon Clark never wrote a book or an article directly on the topic of exclusive psalmody, comments in his writings clearly show his opposition to it.
Clark’s unwillingness to follow his RPCES denomination in the joining and receiving with the PCA in 1982 led him to seek a new denomination. Following this search he wrote to OPC minister Greg Reynold about the various denominational options and, in doing so, noted his opposition both to exclusive psalmody and to idea that instruments are not to be used in worship.
“I did not apply for membership in the OPC. There is so much animosity against me there, I could not face a fight to get in. So I joined the Reformation Presbytery [Covenant Presbytery]– just one Presbytery, almost 25 or 30 ministers scattered from Pa to Florida. I would have been theological[ly] comfortable in the German Reformed Church, but I didn’t know a single person there, and their center is in the Dakotas. They are the ones who refused to merge into the Ev. + Ref. Ch. 25 or 30 years ago. I would have been most comfortable with the Covenanters, but I cannot agree that only Psalms should be sung and that no instruments used. Yet these two points are major + vigorously defended by them. At any rate, I have never enjoyed Presbytery meetings, nor faculty meetings, and I do not expect to play any even half prominent role in my new Presbytery.” – Gordon Clark to Greg Reynolds, 12/9/1983.
In a “Religious Travelogue” written following a long European vacation with his family in 1954, Clark specifically noted his dislike of the musical style used with the Psalm-singing of the Free Church of Scotland.
“The forms of worship in the various countries vary somewhat. The hymns and music of the French churches struck me as noticeably superior to the more jazzy American style. In the German-speaking churches, both of Switzerland and Germany; the music, by reason of a strange succession of major and minor chords, was often difficult and unpleasant, at least to me. The Free Church of Scotland had the worst music of all, led by a precentor without instruments; but it had the best sermons. In England the music was more like our own. In some churches the people stood up to sing and sat down to pray. But usually they stood up for prayer and sat down while singing. On the continent a person upon entering the church would offer a prayer standing, before he sat down. In America we sit down first, and perhaps forget to pray.” – Gordon H. Clark, “Religious Travelogue,” The Witness (c. 1954): 19-20.
The actual arguments against exclusive psalmody in Clark’s writing however are relatively few. Where he writes most at length is on the two verses (Colossians 3:16 and Ephesian 5:19) that refer to “psalms, hymns, and spiritual songs.”
First, in his commentary on Colossians, Clark writes:
“The present writer’s spiritual and physical ancestors, whom he indeed reveres, used this verse in their argument for restricting congregational singing to the Psalms of David. The three terms were supposed to be three divisions of Psalms. But these three titles seem to be insertions in the Septuagint without Hebrew evidence. However that may be, neither this passage nor the parallel in Ephesians speaks of formal congregational worship at all. They rather picture a daily occurrence, presumably at home, or in some cases a workshop owned and operated by Christians. It is an unorganized and spontaneous worship. No doubt it carries implications relative to the assembly on the Lord’s Day; but the Covenanters seem forced to prohibit hymns on a cotter’s Saturday night. At the same time, singing hymns does not imply that the cheap catchy ditties of some modern evangelism, if it is evangelism at all, are superior to the Psalms of David. And a hymn book without a good proportions of Psalms is not fit for a church service.” Gordon H. Clark, Colossians, 1979, 121.
And then more at length in his commentary on Ephesians:
It is a misuse of a phrase in Pliny to conclude that the word each other implies antiphonal singing. In fact the passage does not specifically refer to a church service at all. No doubt it includes church services; we should certainly sing in our weekly worship; but we are also to sing in our homes and social gathering as well. Since the time of the Reformation some Protestant bodies have used this passage to restrict music in a worship service to the singing of the Old Testament Psalms without instrumental accompaniment. The Covenanters are one such group; the Church of Christ rejects musical instruments but does not limit itself to Psalms. The latter group argues, with some plausibility, that the New Testament provides no example of instrumental music in church services, though there may be trumpets in heaven. The Covenanters hold that the words psalms, hymns, and spiritual songs are three divisions of the Psalms, and that hence God approves only of Psalms in church services. The Hebrew text of the Psalms does not make this threefold division. It has been inserted in the Greek LXX. This is a very flimsy support for exclusive Psalmody. On other other hand Meyer’s assertion that ‘the Christian, filled by the Spirit, improvised psalms is clear from 1 Corinthians XIV:15, 26’ is even more flimsy. Nor am I at all impressed with the claim that certain New Testament verses are quotations from early Christian hymns. Something, but not much, can be learned from the usage of the words. Psalmoi of course is the Greek term which gives us the English word psalm or Psalm. Originally the word meant a tune played on a stringed instrument, the sound of a harp. Later it meant merely the song sung. Umnos, our English hymn, meant an ode, particularly the one sung in honor of gods and heroes. Ode (omega with an iota subscript, our English word ode) just means a song. Since psalm originally meant the tune played on a harp and since even the Covenanters admit that the Old Testament approves of the use of musical instruments, it is hard to accept their view that the New Testament has abolished instrumental music. On one occasion I attended a Covenanter church for several Sundays. The auditorium was filled to capacity. The singing was vigorous. The preaching was superb. At the end of the service, either immediately before or immediately after the benediction—I forget which—the congregation burst forth with Psalm 150. It was all new to me, and I could hardly refrain from laughing. Read Psalm 150 and compare, or contrast, what the Psalm commands and what the Covenanters did not do. Not that I wish to ridicule the Covenanters: I with other denominations were half so good. – Gordon H. Clark, Ephesians, 1985, 180-182.
And in Clark’s commentary on First Corinthians he notes of chapter 15, verse 26 (“What then, brethren? Whenever you assemble each one has a psalm, a doctrine, a revelation, a tongue, an interpretation.”):
“Hodge surmises that the ‘psalm’ was not a Psalm of David, but a composition specially prepared for the occasion. The Covenanters would not appreciate this suggestion.” – Gordon H. Clark, First Corinthians, 1975, 2nd Edition 1991, 241.
In all of this Clark must have had a pretty good idea of what the arguments were for Exclusive Psalmody (and anti-musical instruments in worship). He was a minister in two denominations (the UPCNA and RPCGS) which a generation prior had held those positions. Also, at Butler University, Clark worked for some years William Young who was a strong proponent of those views. Yet, he did not come to accept those positions.