composers late into the second half of the twelfth century. A treatise by Guy, Abbot of Chalis, about this time, is concerned with essentially the same problems and presents no really new point of view. He is practically the last of the theorizing organizers. Organum gave way to a new kind of music. In the course of over two hundred years it had run perfectly within the narrow limits to which it had been inevitably confined, and the science of it was briefly this: to devise over any given melody a counter-melody which accompanied it note by note, moving, as far as possible, in contrary motion, sinking to meet the melody when it rose, rising away from it when it fell, and, with few exceptions, in strictest concord of octaves, fifth, fourths, and unison. Rules had been formulated to cover practically all combinations which could occur in the narrow scheme. The restricted, cramped art then crumbled into dust and disappeared. Again and again this process is repeated in the history of music. The essence of music, and, indeed, of any art, cannot be caught by rules and theories. The stricter the rules the more surely will music rebel and seek expression in new and natural forms. We cannot believe that music in the Middle Ages was not a means of expression, that it was not warm with life; and therefore we cannot believe that this dry organum of Hucbald and Odo, of Guido of Arezzo, of Guy of Chalis, which was still-born of scholastic theory, is representative of the actual practice of music, either in the church or among the people. On the other hand, these excellent old monks were pioneers in the science of polyphonic writing. Inadequate and confusing as their rules and theories may be, they are none the less the first rules and theories in the field, the first attempts to give to polyphony the dignity and regularity of Art.