The object of the paper I am about to read is to introduce to your notice some of the principal Italian and Spanish treatises on music of the fifteenth and sixteenth centuries. It is a subject which has never been much attended to in this country, probably on account of the excessive rarity of the works in question; but which possesses a great deal of interest, when viewed in connection with the History of Musical Art. In order to illustrate the subject more fully, I have placed on the table a few of the rarest of these ancient treatises, from my own library, in hopes that some of those who are here to-day may care to examine them, and thus verify the observations I shall have to make concerning them.