The Western hymnody tradition begins with the Homeric Songs, a collection of ancient Greek hymns celebrating the deities of the ancient Greek religions, the oldest of which were written in the 7th century BC. In the 6th century BC, the poet Orpheus composed a set of songs to be sung as he played the lyre. These songs probably had a religious meaning and may have been intended as an initiation ritual into the cult of Apollo. Hymnology is a broad term that describes both the music and the text of a hymn. According to the Oxford Dictionary of Music, "a hymn is a sacred song used for worship or prayer". The word comes from the Greek ὑψινθογραφία (hupsinēgraphia), meaning "writing to the voice", referring to the method by which many early Christians sang prayers and hymns. Today, most people think of a hymn as a solemn musical composition intended for use in church services, but this does not reflect the original purpose of the Homeric Songs or those composed by the early Church fathers. Hymns were also part of the ceremonial rites of various pagan religions. As such, they could be sung as a prayer or invocation to a deity. In Christianity, the term hymn refers specifically to a poem used in worship.