The early Christians maintained the religious practices of their
Jewish background. They continued to worship in the Temple and to
gather for instruction and discussion in the Synagogue, but there
was an increased emphasis upon the sacral meal - now a communal
rather than family meal - frequently referred to as the “breaking
of bread”. Meanwhile, the process of conversion was carried
out in the synagogues and other public places, but the proper ritual
gathering of the faithful was the communal meal, which was
usually held in the home of some Christian prominent in a particular
locality. It is not certain whether every mention in the New Testament
of the “breaking of bread”, or of related terms such as
“the Lord's supper” , refers to a eucharistic celebration,
but certainly many of them do.
The process whereby the Eucharist came to be separated from the
evening meal and was celebrated in the morning, preceded by a discrete
service of instruction, cannot be traced; it is possible to observe
only that this classic pattern is manifested in Justin Martyr's
mid-2nd-century description of the Roman Eucharist.
As for the nature of [singing in these communal gatherings], it
is generally believed that it consisted of newly created material
rather than Old Testament psalms. For example, when Paul
said to the Corinthians “What then, brethren? When you come
together each one has a psalm, has a teaching, has a revelation,
has a tongue, has an interpretation” (1 Corinthians xiv.26-7),
it seems that he was referring to individual contributions of the
congregation.
In addition to the singing of full-length hymns, which would
probably have been performed by individuals, the entire congregation
must have participated in short acclamations and responses.
In the enthusiastic atmosphere of the time, one-word acclamations
like “Amen”, “Alleluia” and “Maranatha”
must have been common, as well as somewhat longer exclamations such
as doxologies or perhaps favorite psalm verses. These
were possibly chanted in response to prayers and readings,
which themselves might have been declaimed rather than read.