The service books of the Ambrosian rite were produced relatively late: the oldest copy of the Manuale, the first to record the texts and some rubrics, dates from the early eleventh century; the earliest redaction of the ordinal, from shortly after 1126; the oldest copy of the antiphoner, which contains the notated melodies of both Mass and Office, from the mid-twelfth. All these books document a liturgy that had been extensively revised after the Frankish conquest of northern Italy in 774. The Frankish reforms did not result in the suppression of the Milanese rite (as they had the Gallican), but many changes were effected, changes that brought the ancient liturgy of northern Italy – without destroying all of its indigenous features – closer to the new, international, Gregorian rite. The purpose of this article is to re-examine the earliest references to the Mass of pre-Conquest Milan and its archdiocese, which reveal more than has been suspected, and to present new evidence concerning the Ambrosian sacrifice as it was in the earliest centuries, even before the time of St Ambrose.

The theory that the antiphon is a kind of refrain and that its original purpose was to be inserted between all the verses of its respective psalm was articulated by Giuseppe Maria Tommasi in the seventeenth century and has been transmitted by liturgical historians with little criticism ever since that time. The present article examines the evidence on which that theory rests, with special attention to the writings of Amalar of Metz, and finds it to be inconclusive or positively contrary to the claims that have been built upon it. The article considers the evidence of antiphonal psalmody at Mass, as transmitted in Ordo Romanus I, and finds support there for the view that antiphons were normally performed only at the beginning and end of their respective psalms. After considering briefly the Liber Pontificalis and the tradition of psalmodic differentiae, the article turns to the treatment of antiphonal psalmody by the liturgical historians Guillaume Durand and Radulph de Rivo in the late Middle Ages and finds in their writings no evidence of a belief that frequent interpolation was the authentic primitive practice. The article concludes that two iterations of the antiphon, once at the beginning and once at the end of the psalm, suited its original thematic intent and that the theory of reiteration after every verse – effectively conflating antiphonal and responsorial psalmody – may be no older than the liturgical scholarship of Tommasi in the late seventeenth century.

Studies of manuscripts such as the Trent Codices (I-TRbc 87–92) and Bologna Q15 (I-Bc 15) have shown that fifteenth-century scribes were not necessarily passive transmitters of the material they copied. Whether motivated by practical constraints or aesthetic preferences, they added, excised and re-composed sections or voices as they saw fit. The frequency and ingenuity of such emendations encourage us to examine them further – not as unwelcome alterations to a putative ‘Urtext’ but as creative acts in their own right.

This article focuses on one site of scribal emendation: the concluding Amen sections of early fifteenth-century Gloria and Credo settings. Frequently, otherwise concordant sources for the same piece transmit Amen sections that appear to be unrelated to each other. I propose that certain types of Amen settings were more susceptible than others to alteration and that one type – the short, self-contained, homophonic Amen – arose through scribal emendation. In order to describe in precise terms the choices a scribe might make, I introduce a nomenclature system for the Amen settings encountered in this period. Taking a panoptic view of the major sources for sacred polyphony in the first half of the fifteenth century, this article contributes to our understanding of scribal activity and manuscript culture.