A processional contains the chants sung in the processions (sometimes also during readings and prayers) that very frequently took place in the Middle Ages. Through the twelfth century these chants were usually still included in graduals and antiphonals. Only afterwards the processional typology became established as an autonomous book. Written in black mensural notation for the Church of Cividale a short while after the half of the fifteenth century, this book is rich in references to other churches of Cividale and to the procession itineraries along the streets of the medieval town. Together with the codex Cividalese CII, for more than one century it has drawn the attention of musicologists and historians of the theatre. The main interest on an international level concerns some ‘dramatic’ compositions of a strong theatrical value. As it has been widely pointed out, among the other things, the codex proposes «the indication of the players’ mimics and gestures for each sentence. From this standpoint it is a unique monument». Moreover there are witnesses of a ‘simple’ archaic polyphony that deserved a dedicated convention (Petrobelli 1980), after which specific studies have increased. The processional liturgy witnessed by this codex also evidences the centrality of the patriarch’s person in local ecclesiastical life: the clergy and people went to meet him with a peculiar chant, the responsory Indicabo tibi homo. In Cividale, according to the indication of the processional CII, f. 60r, the responsory was sung by the clergy: Incipit processio quando itur obviam domino pathriarca, et cum approximatur ei, clerus cantat responsorium.