The name given to a family of Sacramentaries traditionally ascribed to Gregory I (590–604). The most important of these is the book sent by Hadrian I to Charlemagne. The deficiencies in this book were made good from Gelasian service-books current in Gaul. From a fusion of these two sources, ‘Gregorian’ and ‘Gelasian’, the later Roman Missal is derived. The ascription to Gregory I of the book sent by Hadrian cannot be taken literally, as it contained a Mass for his feast, but it has been shown to include material composed by him.