A psalter is a collection of translations of all or part of the Book of Psalms in poetic meter, meant to be sung as hymns in private or corporate worship. Although the Psalms had always had a place of honor in Christian liturgies, the composition and use of metrical psalters became even more important during the Protestant Reformation, especially in its Calvinist manifestation. With the Psalms now in regular meter, and using tunes that all would know, for the first time a large group of untrained singers could learn and sing Biblical texts together. Many Reformed churches adopted the doctrine of exclusive, unaccompanied psalmody; every hymn sung in worship had to be an actual translation of a Psalm or some other Biblical passage. Although the original center of this important movement was in Geneva, the practice of metrical psalm singing during worship was quickly adopted by Protestant groups in Switzerland, Holland, France, England, and Scotland, as well as throughout the Lutheran regions.