For the first mass (ff. 1v-14r), Johannes Martini’s Missa Orsus orsus, which in this source is without attribution and without title,[2] the decorative program is established. It consists of two principal elements: 1) opening discantus initials of main sections of the mass, i.e. the Kyrie, Et in terra, Patrem, Sanctus and Agnus, are illuminated – this is maintained for all masses in the source other than the L’homme armè setting by Faugues; 2) opening letters of voice designations, i.e. Contra, Tenor and Bassus, are drawn in either blue or red ink. This applies to both main sections of the mass and any sub-sections e.g. Qui tollis, Osanna, Agnus [III]. Coloured initials are always used in alternating fashion. The alternating sequence of coloured ink is also used for the second mass, the Anonymous Missa La mort de saint gothard. From the beginning of the third mass on folio 25v, Martini’s Missa Io ne tengo quanto a te, an expanded sequence, but also using blue and red inks, is adopted and this is retained for the remainder of the book.

In this program, for the Tenor, Contra and Bassus voices, opening letters for both voice designation and text are drawn with colour ink. These are always sequential: blue C (for Contra)/red E (for Et), red B (for Bassus)/blue E (for Et) as an example. In following common practice, the upper-most voice is never voice-designated and thus the coloured inked initial is text driven, but always in red. As in the Tabula, the colour ink initials are enhanced with fine-penned filigree.

Neither program is executed without omissions. Interestingly, for the second program even though coloured initials have not been drawn, spaces have been left. Whereas for the discantus of the Missa Orsus orsus Crucifixus, no coloured initial is drawn nor is a space left for inserting the decoration. Here, the C of Crucifixus is written in “standard” script. This is also the case for the Et in spiritum, Osanna [I] and Osanna [II].

Despite these exclusions the decorator has been attentive in his task of elevating the source to one worthy of Ercole’s commission and for inclusion in an expanding repertoire for his chapel singers. Selection of material which is transmitted on folios with a standard set of nine pentagrams draws attention to the source’s Ferrara-centric nature. Most notably of course is the inclusion of eight (from eleven) settings by Johannes Martini – principal composer of both sacred and secular music to the court of Ercole for a period of around twenty-five years. The chapel’s needs or more specifically Ercole’s needs are amply fulfilled with Martini’s two plainsong masses, one for Sundays (the Missa Dominicalis) and one for weekdays (the Missa Ferialis). du Fay’s Missa Ave regina celorum is one of several masses (including for example the Missa Clemens et benigna by Caron) that could serve to underscore Marian celebrations. In contrast to this affiliation is the topical theme of the armed man which is represented by the canonic setting of L’homme armè by Faugues.[3] By way of paying homage to “past masters” is, along with the du Fay mass, the Missa Spiritus almus by de Domarto. Italian secular songs also served as cantus firmi for Martini’s settings of Dio te salve Gotterello and Io ne tengo quanto te. Also included are what might be described as popular masses viz. Martini’s Orsus orsus (either full or in part in seven sources) and Weerbeke’s O venus bant (either full or in part in eleven sources). Clearly decisions were made perhaps by the planner of manuscripts at this time Andrea dalla Vieze to ensure that a broad spectrum of mass repertoire be represented.

By way of conclusion it should be noted that ModE M.1.13 does not only preserve a specifically tailored repertoire for Ercole’s chapel. For the music historian it is also a compendium mass compositional techniques as it provides examples of plainsong quotation and paraphrase, so-called polyphonic chanson masses, canonic structure, iso-rhythmic process, cantus firmus melodies drawn from both well-known and obscure sources as well as many “nut and bolts” procedures. Still to come, maybe ten years after Martini’s death, was Ercole’s last Liber Missarum commission the manuscript now signed as ModE M.1.2 – a choir book preserving seven masses by Obrecht, the Marian mass by Ockeghem Ecce ancilla domine, the Missa Fortuna desperata by Josquin and his super voces musicales setting of L’homme armè.

[2] In this Book, part of the first opening of a mass usually transmits a title under the commencing stave of the Tenor, either stave 7 or 8. In this case (ff.1v-2r) part of folio 1v is now missing from the left-hand side. The letter R (from Tenor) is still visible, however there is no indication that Orsus orsus was included.

[3] A second Liber Missarum was prepared by il fra de san Domenego. Sadly most of this source is lost, but two fragments remain: parts of the Missa Je ne demande by Agricola and the Agnus from the L’homme armè setting by Busnoys; see Lockwood, op. cit., p. 222.