Composed in 1146, Liber Magistri is especially important not only from a historical, paleographic, liturgical and artistic point of view but because it has a complete repertory of Gregorian chant and deals with the history of music, theater, illumination production, medicine, agriculture, and esoteric sciences.
To give an idea of its importance, it’s enough to consider that researchers drew a parallel with “Registrum Magnum”: the value that this latter has for the civil community is the same that “Liber Magistri” has for the religious one.
The miniatures and illuminated initials, adorned with her gold, form a very eye-catching and intriguing feature of the Codex.
Structure of this 12th-century masterpiece
Liber Officiorum is a liturgical book of 452 folios divided into five main sections, covering various subjects:
Calendar (fols.5–30v). An ecclesiastical calendar provides compendiums of astrology, astronomy, medicine, agronomy, and meteorology. Besides, there are illustrations of the various Astrological themes, and it gives instructions for the sowing and harvest seasons, the ripening of the fruit and the breeding of animals.
Officium Divinum (fols.31–148v). We find here a full psalter accompanied by lovely decorated initials, ending with the Litany of Saints, and an enumeration of all the patrons of the city and several of its churches. It also provides music for the parts sung by the choir.
Graduale Placentinum (fols.149–261v). This section commences with a Tonary followed by the chants for the Mass.
Antiphonarium Placentinum (fols.262–439v). Musical-theoretical compilations have been copied on fols. 262–268; the treatises bring together both ancient and modern knowledge on instruments and their use, tones, and execution, and form the background for the performance of a repertoire that is acknowledged by all scholars of the Codex as one of great religious and artistic importance. All the chants for the Office follow on fols. 268v–439v, ending with the corresponding Temporale, Sanctorale and Communio Sanctorum.
Calendarium-Obituarium (fols. 440–445v). The closing part of the Codex, the Obituary, is a calendar listing the benefactors of the Cathedral and is particularly important since it allows us to date the Codex and to explain its genesis.
It is made entirely by hand in full leather with blind toolings. It has raised split cords reproduced on the spine of the facsimile and it's embroidered with big metal bosses.