Most of the medieval music we know today belongs to the last part of the Middle Ages. There was a tradition known as the “Notre Dame school”. This music dates from around 1150 to 1250. It was the time that great cathedrals were being built in Gothic architecture. The cathedral of Notre Dame was a very famous example. The music of this time was called “Ars antique”. It used a system of rhythms called “rhythmic modes”. Gradually a new way of writing was used. This was called “Ars nova” (“New art”). The most famous composer of this time was Guillaume de Machaut. He developed a kind of composition called the isorhythmic motet. He wrote a lot of songs called chansons (the French word for “song”). Other types of song were called "rondeau", "ballade", and "virelai". 