Ars antiqua, also called ars veterum or ars vetus, refers to the music of Europe of the late Middle Ages between approximately 1170 and 1310, covering the period of the Notre Dame school of polyphony and the subsequent years which saw the early development of the motet. Usually the term is restricted to sacred music, excluding the secular song of the troubadours and trouvères; however sometimes the term is used more loosely to mean all European music of the thirteenth century and slightly before.