Wikipedia
Ars antiqua, also called ars veterum or ars vetus, is a term used by modern scholars to refer to the Medieval music of Europe during the high Middle Ages, between approximately 1170 and 1310. This covers the period of the Notre Dame school of polyphony (the use of multiple, simultaneous, independent melodic lines), and the subsequent years which saw the early development of the motet, a highly varied choral musical composition. Usually the term "ars antiqua" is restricted to sacred (church) or polyphonic music, excluding the secular (non-religious) monophonic songs of the troubadours, and trouvères. However sometimes the term "ars antiqua" is used more loosely to mean all European music of the thirteenth century, and from slightly before. The term ars antiqua is used in opposition to ars nova (meaning "new art", "new technique" or "new style"), which refers to the period of musical activity between approximately 1310 and 1375.