The Medieval period lasted from 500AD to the rise of the Ottoman Empire, and was also known as the Dark Ages due to constant warfare. Music during this time was primarily monophonic sacred music like Gregorian chants. Secular music also began to emerge in the 12th-13th centuries in the form of songs performed by minstrels, jongleurs, and poet musicians called troubadours, trouveres, and minnesingers who sang about courtly love and historical events. Notable Medieval musicians included Hildegard of Bingen, a German nun and composer of Gregorian chants, and Adam de la Halle, a French trouvere and innovator of early secular theater.