Greek folk music traditions are said to derive from the music played by ancient Greeks. There are said to be two musical movements in Greek folk music (παραδοσιακή μουσική): Acritic songs and Klephtic songs. Akritic music comes from the 9th century "akrites", or border guards of the Byzantine Empire. Following the end of the Byzantine period, klephtic music arose before the Greek Revolution, developed among the "kleftes", warriors who fought against the Ottoman Empire. Klephtic music is monophonic and uses no harmonic accompaniment.