From the Ninth Century onwards, a new kind of music began to appear, in which the older chants were implemented by additional voice parts of increasingly independent character. The gradual melodic and rhythmic independence of these 'counter parts' led eventually to the rich polyphonic music of the later mediaeval period. From the beginning of the Twelfth Century, the composers of secular song (the knightly troubadours, trouvères and Minnesingers) and of vocal and instrumental dance music also began to make use of polyphonic settings. The climax of this development of polyphony was reached in the French Ars Nova of the Fourteenth Century, with Guillaume de Machaut (died 1377) as its leading master.