The history of Western music properly begins with the music of the Christian Church. But all through the Middle Ages and even to the present time men have continually turned back to Greece and Rome for instruction, for correction, and for inspiration in the several fields of work this has been true in music, though with some important differences. Roman literature, for example, never ceased to exert influence in the Middle Ages, and this influence became much greater in the fourteenth and fifteenth centuries when more Roman works became known at the same time, too, the surviving literature of Greece was gradually recovered. But in literature, as well as in some other fields (notably sculpture), medieval or Renaissance artists had the advantage of being able to study and, if riley so desired, imitate the models of antiquity. The actual poems or statues were before them. In music this was not so. The Middle Ages did not possess a single example of Greek or Ro man music--nor, it may be added, are we today much better off. About a dozen examples--half of them were fragments of Greek music have been discovered, nearly all from comparatively late periods, but there is no general agreement as to just how they were meant to sound there are no authentic remains of ancient Roman music. So we, as well as the men of medieval times, derive nearly all our knowledge of this an in the ancient civilizations at second hand from a few rather vague accounts of performances, but mostly from theatrical treatises and literary descriptions. The influence of Greece and Rome became greater in the fourteenth and fifteenth century because ______.