Liber misticus (type of manuscript with chants, readings and prayers for the Old Hispanic cathedral cursus, i.e. for vespers, matutinum and mass, and, on penitential days only, also for the hours of tertia, sexta and nona) with material for Eastertide. Some of its folios are missing, including those that were at its beginning: it starts at the end of the mass for Easter Sunday. Previous authors (e.g. VIvancos, 2007) have proposed that this is a misticus made of two mistici, one using a column per page and another one using two columns per page. However, it is also possible that the two formats corresponded to two different scribes writing the same book, or two moments of production of the same book; moreover, there is a folio with texts written in both one-column and two-column layout (see e.g, f. 75v). This manuscript has musical notation (Old Hispanic vertical but already somewhat tilted towards the right, in a fashion similar to that of the Old Hispanic horizontal notation) in a few chants only (ff. 53r-54v) despite the fact that its chant texts were written leaving enough space to include the music. This misticus is one of the few that has sermons - it has a "sermo de cotididie" (sic, see ff. 132r-135v). After the misticus there is part of the passion of Saint Juliana, copied in what seems to have been the last folios of this misticus and thus originally left in blank (ff. 173r-v). It might have been added after the suppression of the Old Hispanic rite, since no Old Hispanic proper office or passion of this saint has surfaced.

Date: the fact that it seems to be an unfinished book suggests that it was copied near the time of the official suppression of the Old Hispanic rite (Council of Burgos, 1080), that is, around the second half of the eleventh century, before 1080. The fact that a passion of a saint (Juliana) that did not have an Old Hispanic proper office was added to its folios in blank also points to a liturgical observance that was no longer Old Hispanic. Despite this, only Vivancos (2007) and the British Library (2017) give as its copy-date the beginning of the eleventh century, while most authors date it as tenth century (Clark, 1920; García Villada, 1923; Millares Carlo, 1961 and 1999; Pinell, 1965; Brockett, 1968; Randel, 1973; Gómez Muntané, 2001; Asensio, 2003). Other dates are: tenth or eleventh century (Férotin, 1912; Rojo and Prado, 1929; Fernández de la Cuesta, 1980; González Barrionuevo, 1992); ff. 1r-172v, early-eleventh century, and ff. 173r-v, early-tenth century (Díaz y Díaz, 1983, these dates are debatable because the material in 173r-v was in all likelihood added after the production of the rest of the manuscript, as mentioned above). Walker (1998) dates it as eleventh century "probably significantly later than" GB-Lbl Add MSs 30844 and 30845 (which she dates as eleventh century)

Origin: this manuscript was at the Abbey of Santo Domingo de Silos until it was sold to UK owners in the nineteenth century, but it contains no proof of the place where it was copied. González Barrionuevo (1992) proposes that the little musical notation in this manuscript was added to it in the scriptorium of Silos.

Liturgical tradition: A.

Randel responsorial tone tradition: unknown because it lacks responsorial verses.