Most folios of this manuscript (ff. 1-172v), belonged to a liber misticus (type of Old Hispanic manuscript with chants, readings and prayers for the cathedral cursus, i.e. vespers, matutinum and mass, and, only on penitential days, also the hours of tertia, sexta and nona), with several lacunas. Its ff. 1773r-177v have canticles and have thus been classified as part of a liber canticorum (Pinell, 1965); only this last section has musical notation.

This manuscript has the only surviving misticus with sermons for all of its offices. It begins in the middle of Idelfonsus of Toledo's De uirginitate perpetua beatae Mariae, which was read in the vigil of the office for Saint Mary. F. 32v has the first vespers of this office followed by the rest of its services (matutinum, mass and second vespers). Until f. 110v it has no important lacuna (presenting the offices of Saint Thomas, Christmas, Saint Stephen, Saint Eugenia, Saint James, Saint John Apostle and Saint Columba of Sens). After this there is a lacuna: f. 111r starts at the end of first vespers of the Circumcision office which is incomplete also at its end (f. 124v, with the Pater Noster and Benedictiones of the mass and the second vespers missing). After this we find another lacuna: the office of Initio Anni and the beginning of the Epiphany office are missing. F. 125r has the Epiphany office, starting halfway through the first prayer of the sixth missa of its matutinum; it has the full mass until f. 137v. Here there is another lacuna: all offices from the Epiphany (6 January) to the Chair of Saint Peter (22 February). Ff. 138r-148v has the Chair of Saint Peter office. After this there is another lacuna: all offices between the Chair of Saint Peter and the Ascension of the Lord are missing (i.e. the end of Christmastide, all Lent and great part of Eastertide). Ff. 149r-167r have the Ascension office. In f. 167v an "OFF[FICIU]M D[E] LETANIAS ANTE PENTECOSTEN" was copied in an unusual place (all other Old Hispanic manuscripts preserving these Litanies have them after the office for the Sunday after the Ascension); this office consists of just one vespers and was written there very likely to take advantage of the available parchment. After this there is another lacuna: f. 168r starts in the middle of the mass of the office for the Sunday after the Ascension. After the end of this mass, in f. 170v, there are readings for the office of the Canonical Litanies, also copied here in an unusual placement - other manuscripts have these Litanies in November, so perhaps this litany was added later or trying to make the most of available space in the manuscript. The liber canticorum in ff. 173r-175v has cantciles 2-7, and 10-15, according to Brockett, 1968.

Date: the fact that the misticus includes sermons and lacks musical notation, despite the fact that the text of all of its chants were copied leaving enough space for the music (it seems to be unfinished), strongly suggests that this manuscript was copied at a late date, near the official suppression of the Old Hispanic rite (Council of Burgos, year 1080). The inclusion of material for litanies offices in unconventional placements within the manuscript, give the impression of a scribe hastily writing down liturgy that only existed in the Old Hispanic rite and that was about to disappear. Previous authors have dated it as tenth century (Clark, 1920; García Villada, 1923; British Museum, 1968; Randel, 1973; Fernández de la Cuesta, 1980; Gómez Muntané, 2001); early-tenth century (Vivancos, 2007, but also quoting Millares Carlo's eleventh century date); late-tenth century (Gros, 1978); tenth to elevent century (British Library, 2017); eleventh century (Férotin, 1912; Millares Carlo, 1961 and 1999; Díaz y Díaz, 1983; Walker, 1998). Some authors believe that the liber canticorum section is earlier, i.e. late-ninth to early-tenth century (García Villada, 1923; Pinell, 1965; Díaz y Díaz, 1983), or tenth century (Brockett, 1968).

Origin: it was preserved at the Abbey of Santo Domingo de Silos for several centuries until it was sold in the nineteenth century to UK owners. Díaz y Díaz, 1983 believed that it was copied in this abbey but that its ff. 173r-177v were not from there but from the East of the Iberian Península, probably from La Rioja or from a scriptorium with influences from La Rioja. There are no definitive proofs for any of the proposed provenances.

Liturgical tradition: A.

Randel responsorial tone tradition: unknown (not enough notated responsorial tones).