Classical music is art music produced or rooted in the traditions of Western culture, including both liturgical (religious) and secular music. While a more precise term is also used to refer to the period from 1750 to 1820 (the Classical period), this article is about the broad span of time from before the 6th century AD to the present day, which includes the Classical period and various other periods. The central norms of this tradition became codified between 1550 and 1900, which is known as the common-practice period. European art music is largely distinguished from many other non-European classical and some popular musical forms by its system of staff notation, in use since about the 11th century.[not in citation given] Catholic monks developed the first forms of modern European musical notation in order to standardize liturgy throughout the worldwide Church. Western staff notation is used by composers to indicate to the performer the pitches (which form the melodies, basslines and chords), tempo, metre and rhythms for a piece of music.