One of the reasons why music did not take a central place in early Christian worship is that the central element of their meetings was the sharing of the bread and wine, the Communion or Eucharist, whether in the context of a church service or in the agapé, the 'love feast' in homes. Ignatius was made bishop of Antioch in AD 67, when many of the apostles were still alive and active, and he describes the Christian church as "a Eucharistic community" which realised its true nature when it celebrated Communion.
In turn, this emphasis might be due to the belief among first generation Christians that the sharing of the bread and wine was to be done "until Jesus returns", which they believed would be soon, perhaps in their lifetime. When this did not materialise, a Christian liturgy for worship began to develop, described for us by early apologists like Justin Martyr and Hippolytus. It involved greeting, reading from scripture, responsive (antiphonal) singing, baptisms, a sermon, prayers, the offertory, the communion and a blessing.
The first hymn with actual musical notation which we possess, the "Oxyrhynchus hymn", is from the 3rd century. At the same point, the Apostolic Tradition, attributed to the theologian Hippolytus, shows that the singing of psalms with Alleluia as the refrain was a feature of early Christian agape feasts.
It wasn't until around 375 that antiphonal singing of psalms became popular in the Christian East; in 386, Ambrose of Milan introduced this practice to the West. Around 410, St. Augustine described the responsive singing of a psalm at Mass. Sources are few and inconclusive regarding how Christian chant / song developed, but we do know that by 678, Western (Roman) chant was being taught at York. Distinctive regional traditions of Western plainchant arose during this period, notably in the British Isles (Celtic chant), Spain (Mozarabic), Gaul (Gallican), and Italy (Old Roman and Ambrosian).
We can safely say that by this stage, sung worship was an established part of Christian services, albeit without instruments. For the arrival of the earliest church organs we must wait until the mid-11th century.
