Calvin did not simply prefer plain church music, he removed an entire category of it. Geneva's churches took their organs out of service under the Reformation, and Calvin's own writing on worship treats elaborate polyphony as a danger rather than an ornament: music that draws the ear to its own complexity, he argued, pulls attention away from the words being sung and toward the skill of the singers performing them. His remedy was not silence but a specific, disciplined alternative. Every psalm would be set to a single unadorned melodic line, sung by the whole congregation together in unison, in French rather than Latin, with no instrument and no trained choir standing between the worshiper and the text.
This broke sharply with the century's other reformers as much as with Rome. Martin Luther wrote original hymn texts of his own and kept a role for the organ in Lutheran churches; Huldrych Zwingli, further to the theological left in Zurich, removed music from congregational worship almost entirely rather than reshape it. Calvin's position sat between the two: song belonged in worship, but only the biblical psalms themselves, in a form every member of the congregation, literate or not, trained singer or not, could learn and carry. The Genevan Psalter was the practical instrument of that theology, commissioned expressly to give a congregation something to sing rather than something to listen to, and the discipline of unaccompanied unison psalm singing it established held across Reformed churches for roughly two centuries after Calvin's own death.