Around 500 A.D., western civilization began to emerge from the period known as "The Dark Ages," the time when invading hordes of Vandals, Huns, and Visigoths overran Europe and brought an end to the Roman Empire. For the next ten centuries, the newly emerging Christian Church would dominate Europe, administering justice, instigating "Holy" Crusades against the East, establishing Universities, and generally dictating the destiny of music, art and literature. During this time, Pope Gregory I is generally believed to have collected and codified the music known as Gregorian Chant, which was the approved music of the Church. Much later, the University at Notre Dame in Paris saw the creation of a new kind of music called organum. Secular music was sung all over Europe by the troubadours and trouvères of France. And it was during the Middle Ages that western culture saw the arrival of the first great name in music, Guillaume de Machaut.