Processions, thus far, have been thought of chiefly, as wholly or in part outside the church edifice. Processions within the edifice were also frequently observed. A procession of the clergy, in connection with which psalms and antiphons were sung, preceded the Sunday high mass; another took place as the Gospel codex was carried to its place for reading. Other ceremonies within the church, aside from the liturgy proper, were sometimes accompanied by hymns.[19] Perhaps the earliest hymn in use at a special ceremony, once more a selection from the hymnal, was _Audi, iudex mortuorum_ (_A. H._ 51. 80), “Hear Thou Judge of the dead,” sung on Holy Thursday at the consecration of the chrism.[20] The words _O redemptor, sume carmen temet concinentium_, “O Redeemer, accept the hymn of Thy people magnifying Thee,”[21] formed a refrain, a metrical feature which came to be the unmistakable mark of the processional hymn. In this early period from the sixth to the tenth century, a new idea and a new practice came into being, the use of hymns apart from those of the canonical hours and the sequences of the mass. The ninth century revival of hymnody in all its branches was taking place in western Europe just as this period came to a close, in connection with which the processional hymn was inevitably affected as the office hymn and the sequence had been by a fresh inspiration to poetry and worship. The movement came to fruition at St. Gall where the musical and ceremonial aspects of that great monastic center were so highly developed, a center which had contributed so heavily to the Carolingian revival of literature and the arts. The French liturgical scholar, Leon Gautier, whose contributions to the study of medieval hymnology have already been mentioned, was the first to identify the processional hymn as a trope or liturgical interpolation. In a study of the St. Gall processional hymns he observed that they were classified by the name _versus_ which in itself points to a separate hymnic category. Other earlier hymns used in processions were there called _versus_. Gautier discovered that musical notation always appeared with the _versus_, an indication that these hymns were invariably chanted and he noted that the _versus_, in the manner of the hymn _O redemptor, sume carmen_, cited above, was without exception, accompanied by a refrain.[22] The processional hymns of St. Gall, like the sequences, bore the characteristic marks of the hymnic group to which they belonged. From this stage in their evolution they were set apart by their music, classification and refrain. The wider circle of Carolingian liturgical interest included hymn writers other than those of St. Gall: Theodulphus of Orleans, Walafrid Strabo of Reichenau, Rabanus Maurus of Fulda, Radbert of Corbie, who with Waldram and Hartmann of St. Gall wrote processional hymns. The hymns of Theodulphus and of Rabanus Maurus have been considered above.