About three years ago I had the privilege of reading a paper before this Association “On the Early Italian and Spanish Treatises on Counterpoint and Harmony.” At that time I had almost made up my mind not to carry on my remarks beyond the limits of the sixteenth century. I said that “the reason I had given no specimens of works of the seventeenth century was that it was about that time that modern tonality took its rise, mainly through the innovations introduced by Monteverde, and that the art was thus revolutionised.” At the same time I thought that perhaps “on some future occasion I might be allowed to trace the progress of the art down to more recent periods.” This further history of the theoretical development of the art of music is the subject on which I wish to enlist your kind attention to-day. It is by no means so easy to treat of this later period as it was of the earlier, because so many treatises were published in the seventeenth century that the task of selection becomes very difficult, and also because some musical facts and theories are involved which have no small bearing on controversies still under discussion at the present day. Before the seventeenth century modulation from key to key, as we now understand it, did not exist. Indeed, there could hardly be said to be any really fixed tonality beyond that of the old ecclesiastical scales, to which all music was rigidly conformed, except indeed such rustic melodies and dance-tunes as had escaped the influence of the scholastic theories then in vogue.