Gregorian chant
The New Testament, tells how Jesus and his friends sang together: "When they had sung the hymn, they went out to the Mount of Olives" (Matthew|26.30). Other writers from those early centuries such as Pope Clement I also said that Christians sang religious songs, but they don’t tell us what the music sounded like. The "Oxyrhynchus hymn," a 3rd-century Christian Greek song, has lasted with written musical notes, but we do not know if this song is connected to plainchant.