The writers and literary leaders of the Carolingian period were by virtue of their clerical profession actively engaged in liturgical studies. Alcuin compiled the missal which established the Gregorian Sacramentary in Frankish realms and constituted a recension acceptable to the Roman Church.[7] A significant innovation for hymnology was the decorative procession.[8] Alcuin was also influential through his devotional works which supplemented the public worship of the mass and offices. Paulus Diaconus and Angilbert were second to Alcuin in promoting liturgical studies. The works of the great writers were accompanied by numerous writings of lesser importance which bear witness, as will be evident below, to the increasing practice of hymn-singing. The influence of the Roman Rite, largely barren of hymns, was at the same period, in contact with the influence of Benedictine precedent in hymn singing which in the end prevailed. The Latin poetry associated with the Carolingian era has been edited and published in a monumental form under the title _Poetae Latini Aevi Carolini_.[9] The collection, produced in the spirit of a classical revival by a circle of court poets, includes secular as well as religious verse. Carolingian culture not only in the specific field of literature but in the broader sense afforded a medium for the spread of Celtic, Byzantine and Germanic genius. The Celtic portion of the poetry in the early monastic cycles has already been described in connection with the _Old Hymnal_. Prior to the eighth century, a transfer of Celtic scholarship to the continent began to take place. The missionaries, Columbanus, Gall, Foilan, Disibod and others, came first, during the seventh and eighth centuries. Refugees, fleeing before the Norse invasions of the late eighth and ninth centuries, followed. Wanderers and pilgrims crossed the Channel, among them _peregrini_ who left their homeland to live in new countries as a means of spiritual satisfaction and reward. Scholars came also who hoped for a more sympathetic reception for their teachings among the continentals.[10] On the whole, Celtic immigrants found a welcome. Charlemagne himself favored them.[11] Celtic teachers were proficient in orthography, grammar, Greek, scriptural and liturgical subjects and the arts.[12] They brought with them manuscripts, the influence of which was felt, not only in their subject matter but in musical notation and characteristic scripts.[13] The Bangor Antiphonary, the hymns of which have already been considered, came to the continent at this time. Among the famous teachers of music was Marcellus[14] who, at St. Gall, instructed Notker, Tutilo, Waltram and Hartmann, a fraternity devoted to finer ecclesiastical music and hymnody.