The Leiden choirbooks are six volumes of polyphonic renaissance music of the Franco-Flemish school copied for the Pieterskerk, Leiden and now preserved at the Erfgoed Leiden en Omstreken (formerly Gemeentearchief Leiden). The Liturgy of the Hours in major Dutch churches in the 15th Century was as follows: * Matins * including Lauds (one combined service) * Prime, early morning * Terce, mid-morning * Sext, midday * None, mid-afternoon * Vespers, evening service * Compline, night service