As we saw several synods in the 16th century and the National Synod of Dordtrecht in 1619 decided that only Datheen’s psalms were allowed in worship. On this ground it has many times been asserted that Calvinists in the Netherlands did sing psalms only and no other chants. In Römling’s writings we see–and other sources affirm this–that decisions made by synods are not very good sources for our knowledge of actual liturgical practice. In many parts of the Netherlands congregations were singing also hymns other than those of Datheen’s psalter, mostly hymns of Lutheran origin, until far into the nineteenth century. But even when we had no other sources than decisions made by synods, the facts would still be clear. For the more often a decision is repeated, the more probable it is that it was ignored. This means that when Dutch synods decided several times that Datheen’s psalter should be used in the services, this repeated regulation was necessary in the opinion of the members of these service, this repeated regulation was necessary in the opinion of the members of these synods to change a different practice! Such decisions are therefore not to be understood as a report of an actual situation.
—Jan R. Luth, “Remarks on the History of Congregational Singing in the Dutch Reformed Churches” in Omnes Circumadstantes: Contributions Towards A History of the Role of the People in the Liturgy ed. Charles Caspaers and Marc Schneiders (Kampen: J. J. Kok, 1990), 193.