How did the Christian choir develop from congregational singing?

In the early Christian Church, music for the mass was performed by both the priest and the congregation. Over time, a specialized group of singers emerged from the congregation to assume the role of answering and contrasting the priest's solo singing; this group became known as the choir.1

For many centuries, the role of these choirs was restricted to the unison singing of plainchant. During this period, polyphony was considered the exclusive preserve of soloists because early musical notation lacked the precision required for choral performance of multipart music.23

This dynamic shifted as musical theory and notation improved, allowing choirs to perform more complex works. By the 15th century, the mass became a vehicle for choral performance, and the alternation between soloists and the full choir became a standard practice. This evolution was further encouraged by the growing wealth of the church and the establishment of formal institutions, such as the schola cantorum, which trained singers in both technique and repertory.234