In the 15th and 16th centuries, the rediscovery of ancient Greek and Roman culture⎯Humanism⎯had a tremendous impact on European cultural, intellectual, and political history. The ancient Greek ideal of music as a power that can change nature and move souls profoundly influenced composers of the Renaissance. We will examine that influence in theory and practice through the ideas of the ancient Greek mathematician Pythagoras, the concepts of musica reservata and word painting, and the evolution of a system of tonal harmony. The music of the mid-Renaissance is represented by the French composer Josquin Desprez.