Since the late middle ages "evensong" has been the popular name for vespers (from the Latin vesperis, "evening"), the Evening Office of the western church. Cranmer used it in the 1549 BCP. Although in 1552 he replaced it with "Evening Prayer," the common name remains "evensong." In many Anglican cathedrals and other large churches, especially in England, evensong is sung by clergy and choir as a choral liturgy. See Evening Prayer.
Glossary definitions provided courtesy of Church Publishing Incorporated, New York, NY,(All Rights reserved) from "An Episcopal Dictionary of the Church, A User Friendly Reference for Episcopalians," Don S. Armentrout and Robert Boak Slocum, editors.