During the early history of Christian worship the churches were spread through many countries in the Roman Empire. The musical traditions that already existed in these countries were used, so there was great variety. Musical instruments were associated with the devil and with dancing, and so they were thought to be wicked and were not allowed in churches. The only music that was allowed in churches was singing. In the 4th century Bishop Ambrosius of Milan introduced the antiphon and encouraged newly composed hymns. Psalms were an important part of the early Christian worship. Responsorial psalms were psalms which were sung by one person (who may have been called a “reader”), and the congregation may have responded at the end of a verse with something simple such as “Alleluia”. Gradually “antiphonal psalmody” was developed. This meant that the choir stands on opposite sides facing one another and they sing the verses of the psalm alternately (first one side has a turn, then the other). Antiphonal psalm singing can still be heard today in Anglican cathedrals.