In this source the folios have been numbered twice, both times in the upper right hand corner of each recto. The index follows the second, smaller set of numbers (generally written to the left of the older, larger numbers), which corrects two mistakes in the other set (f. 34 was omitted and 208 was used twice). Some sections of the manuscript are extremely difficult to read, especially at the beginning (ff. 1-10) and the end (ff. 278-281). In these sections it has been necessary to represent some incipits as incomplete or illegible and to place question marks in the columns that would ordinarily specify mode or differentia. Partial reconstruction of the contents of some of the most severely damaged folios of the source was facilitated by two important editions of chant texts, those presented in volumes 3 and 4 of CAO and those published in Ottosen's study of responsories for the Office of the Dead (see below). There are clues to the identity of some responsories for Matins on the First Sunday of Advent (notated on folios now missing from the manuscript) in the incipits listed for Matins on Annunciation (f. 160r). Some of the unusual Offices in this source may be found in Analecta hymnica or in other CANTUS indices. The Office for Trophimus, Bishop of Arles (ff. 132r-135v) was edited from a 16th- century printed breviary in Analecta hymnica vol. 18, p. 95ff (LMLO TR61), but is found here in a more complete version including antiphons for Matins, for the psalms of Lauds, and for second Vespers. The Office for Thomas Becket has been edited in Analecta hymnica vol. 13, pp. 92ff (LMLO TH21). Among other unusual Offices are those for Victor, after whom the monastery of St. Victor in Marseilles is named, and his three soldier- companions (ff. 179r-183r); John Cassian, the founder of St. Victor (ff. 186r-187r); Martha, sister of Lazarus (ff. 187r-191r); Romanus of Antioch (ff. 230v-231r); and Lazarus of Bethany (ff. 249r-253r). For certain other liturgical occasions the cycles of chants that are provided resemble those of Beneventan manuscripts (as represented by Benevento V-21, Hesbert's manuscript L): see, for example, Mary Magdalene (ff. 183v- 186r); and the Transfiguration (ff. 195v-199r). The differentiae are labeled with a letter in the left-hand column of the differentia field; this letter indicates the ending pitch of the differentia (ignoring transposition). When more than one differentia in a mode ends on the same pitch, the second and subsequent differentiae are indicated by a number after the letter. The tonus peregrinus is indicated by "P" in the right-hand column of the differentia field. These differentia names are applied to the same "saeculorum amen" formulas in all of the Aquitanian sources indexed by CANTUS (Paris, lat. 1090, Toledo 44.1, and Toledo 44.2), hence there may be gaps in the numbering. Thus, differentia 1.D in the index for Toledo 44.2 and differentia 1.D in Paris, lat. 1090 refer to identical formulas. (This naming system is not carried over to sources that are not Aquitanian.)
In some cases, a lower-case letter appears in the "extra" field to the right of the differentia field. This indicates variations in the differentia, usually of neumation. These letters indicating variants refer only to one particular source, and (unlike the differentia names themselves) are not applied to the other Aquitanian sources to indicate the same variant.
- Collamore, Lila. "Aquitanian Collections of Office Chants: a Comparative Survey." Ph.D. dissertation, The Catholic University of America, 2000.
- Hughes, Andrew. Late Medieval Liturgical Offices: Resources for Electronic Research. Vol. 1, Texts. Subsidia Mediaevalia, 23. Toronto: Pontifical Institute of Mediaeval Studies, 1994.
- Ottosen, Knud. The Responsories and Versicles of the Latin Office of the Dead. Aarhus, Denmark: Aarhus University Press, 1993.