Jazz music can be traced back to the early 1800s. At this time there were almost half a million Sub-Saharan Africans working as slaves in United States. Coming mostly from the West of Africa and the Congo Basin, they brought with them many African music traditions. An easily recognisable tradition is the counter-metric structure, a tradition which has had a huge impact on jazz music. They also used traditions such as the call and response structure when working or carrying out rituals. Their music differed from European music in many ways; the overall structure, rhythym, harmonies - African music did not feature any harmonies (unless in the circumstances of accidental harmonies due to singing a major 3rd out of tune, but the chances of this are quite low... Nobody is that lucky). African music tends to stick to single-line melodies. Although, there was never a lack of people at rituals so it wasn't as if there weren't enough people to sing both melodies and harmonies. Up until 1843, slaves in New Orleans would meet on Sundays at Congo Square. There they would have African dance festivals which were accompanied only by drums. These festivals were very popular and soon spread all around the USA. These festivals stopped taking place possibly because of the growing opposition to slavery in America.