Organ Chorale; Chorale Prelude

A polyphonic composition for organ based on a chorale melody (excluding simple harmonizations such as those suitable for accompanying congregational singing).  Although the term is commonly used only for the polyphonic settings of German Protestant chorales, the earlier organ settings of hymns of the Roman Catholic Church must also be considered.

In the German Protestant Church the organ chorale assumed a role quite different from that in the Roman Catholic service.  In the latter, it served as a substitute for plainsong, from which it inherited its liturgical function.  In the Protestant Church, the singing of the chorale became the privilege of the congregation, and it was the organist's duty not only to accompany the singing but also to play the chorale beforehand on the organ as an introduction (hence the German organ chorale is called a chorale prelude).