Meanwhile the Folk-song, already mentioned in its primogenial character, reasserted itself as the annotator of lyric poetry, through the activity of the troubadours from the eleventh to the fourteenth centuries. Of these, the name of Adam de la Hale is, of course, best known. Just as combined Oriental and Greek traditions formed the substructure of the early ecclesiastical modes, so a fusion of the Gregorian Chant and the Folk-song resulted in the establishment of a second, and in this case more distinctly accretive nucleus. This was of incalculable service, primarily to subsequent secular music as a whole, eventually to instrumentation as a side issue. For the soul of the Folk-song finds expression in the melodic. And this natural mode of expressing natural emotion, amplified not alone by the peoples of the Romance nations and of the Teutonic races, but also quite especially by such as were of Celtic origin, infused life, color, and variety into the stiff and formal church style then in vogue. Again, _la gaie science_ required the art of accompaniment; consequently this long-neglected acquirement began to awake from its lethargy. So we find the troubadours accompanying their songs with a variety of instruments such as the crwth, the rebec, the lute, the harp, the viol. The Folk-song has in the end proved to be the most enduring mode of expressing feeling, representing, as it does, the natural growth of a nation. Influenced by local temperament, climate, history, on every hand its distinctly indigenous characteristics have stood out in peaceful contrast to the eclectic polyphony of coexisting scientific attempts. And, as we know, although the Folk-song was eclipsed for a time by other forms, it was destined to play an important rôle. For its loftiest mission was realized not only in connection with the German Singspiel of the eighteenth century, but also through its application by the great classicists of the same period as contrasting theme for the Sonata-piece. IV. Continuing our chronological review, we trace the propagandism of Italian theoretical principles through France into the Netherlands. Here, during the fifteenth and early sixteenth centuries, polyphonic vocal music was reared on the exalted pedestals of noble Gothic architecture. From Dufay--the connecting link between the French and Flemish Schools--through Ockeghem, Josquin des Près, Willaert, to Lasso, the supremacy of musical composition was conceded to the Low Countries, although simultaneous musical activity in Italy was by no means retrogressional. As for the labors of such men as Dunstable in England and Isaak in Germany, the former was not in the direct line either of technical or of æsthetic evolution, whereas the latter was trained in Italy and wrote in the Flemish style.