7. MUSIC. Unlike the other studies of the _Quadrivium_, the instruction in music was quite extensive, and from early times a good course in musical theory was taught (R. 74 f). Boethius' _De Musica_, written at the beginning of the sixth century, was the text used. Music entered into so many activities of the Church that much naturally was made of it. The organ, too, is an old instrument, going back to the second century B.C., and the organ with a keyboard to the close of the eleventh century. This instrument added much to the value of the music course, and the hymns composed by Christian musicians form an important part of our musical heritage. [11] The cathedral school at Metz and the monastery at Saint Gall became famous as musical centers, and of the work of one of the teachers of music at Saint Gall (Notker) it was written by his biographer: "Through different hymns, sequences, tropes, and litanies, through different songs and melodies as well as through ecclesiastical science, the pupils of this man made the church of God famous not merely in Alemannia, but everywhere from sea to sea." [Illustration: FIG. 47. AN EARLY CHURCH MUSICIAN (From a fourteenth-century manuscript, now in the British Museum)] THE GREAT TEXTBOOKS OF THE MIDDLE AGES. While the textbooks mentioned under the description of each of the Liberal Arts formed the basis of the instruction given, most of the instruction before the twelfth century was not given from editions of the original works, but from abridged compendiums. Six of these were so famous and so widely used that each deserves a few words of description. 1. _The Marriage of Mercury and Philology_, written by Martianus Capella, between 410 and 427 A.D., was the first of the five great mediaeval textbooks. Mercury, desiring to marry, finally settles on the learned maiden Philology, and the seven bridesmaids--Grammar, Dialectic, Rhetoric, Geometry, Arithmetic, Astronomy, and Music--enter in turn at the ceremony and tell who they are and what they represent. The speeches of the seven maidens summarized the ancient learning in each subject. This textbook was more widely used during the Middle Ages than any other book. 2. _Boethius_ (475-524) was another important mediaeval textbook writer, having prepared textbooks on dialectic, arithmetic, geometry, music, and ethics. Nearly all of what the Middle Ages knew of Aristotle's _Logic_ and _Ethics_, and of the writings of Plato, were contained in the texts he wrote. His _De Musica_ was used in the universities as a textbook until near the middle of the eighteenth century. 3. _Cassiodorus_ [12] (c. 490-585), in his _On the Liberal Arts and Sciences_, prepared a digest of each of the Seven Liberal Arts for monastic use, fixing the number at seven by scriptural authority. [13]