Byzantine music was established in the early years of Christianity and influenced by ancient Greek music. It has remained largely unchanged over the centuries and is closely tied to Orthodox religion, being used to accompany hymns praising God. Byzantine music is characterized by unaccompanied singing by choirs and uses the system of the eight modes to compose hymns. While it was initially influenced by European polyphonic styles, Orthodox churches later established schools to preserve the traditional monophonic nature of Byzantine music. Today it can be learned in churches, monasteries, and conservatories.