A metrical psalter is a kind of Bible translation: a book containing a verse translation of all or part of the Book of Psalms in vernacular poetry, meant to be sung as hymns in a church. Some metrical psalters include melodies or harmonisations. The composition of metrical psalters was a large enterprise of the Protestant Reformation, especially in its Calvinist manifestation. Biblical basis During the Protestant Reformation, a number of Bible texts were interpreted as requiring reforms in the music used in worship. The Psalms were particularly commended for singing; James 5:13 asks, "Is anyone happy? Let him sing songs of praise." Colossians 3:16 states "Let the word of Christ dwell in you richly as you teach and admonish one another with all wisdom, and as you sing psalms, hymns and spiritual songs with gratitude in your hearts to God." Various Reformers interpreted these texts as imposing strictures on sacred music. The psalms, especially, were felt to be commended to be sung by these texts. The need was felt to have metrical vernacular versions of the Psalms and other Scripture texts, suitable to sing to metrical tunes and even popular song forms. Following an interpretation of the regulative principle of worship, many Reformed churches adopted the doctrine of exclusive psalmody: every hymn sung in worship must be an actual translation of a Psalm or some other Biblical passage. Some Reformed churches, especially the Calvinists, rejected the use of instrumental music and organs in church, preferring to sing all of the music a cappella. Even today, the Reformed Presbyterian Church of North America, the Free Presbyterian Church of Scotland, and other Reformed churches of the Scottish tradition maintain this practice. The psalters themselves During the pre-reformation days, it was not customary for lay members of a church's congregation to communally sing hymns. Singing was done by the priests and other clergy; communal singing of Gregorian chant was the function of professional choirs, or among communities of monks and nuns. John Calvin, inspired by Erasmus's comments, desired singable versions of the Psalms and other Christian texts for the communal use of the Reformed churches. The Genevan Psalter One of the greatest metrical psalters produced during the Reformation, the Genevan Psalter, was authored for the Protestant churches of France and Geneva (called the Huguenots). It has been in uninterrupted use to the present day by the Huguenot and other French-speaking Protestant churches. The