Boethius, De musica, f.43v, (211 x 144 mm), 12th century -This is a manuscript about the theory of music. It was copied probably in England at Christ Church, Canterbury, in the second quarter of the twelfth century. Its main focus is the mathematical basis of music - Alexander Turnbull Library, MSR-05., via Flickr.
the Chludov Psalter (mid-9th century CE) is a rare testimony of Byzantine art at the time of the Iconoclasm. In fact, it is one of only 3 illuminated Byzantine Psalters to survive from the 9th century.