 With eight or more polyphonic voice parts to keep track of in performance, works in polychoral style required some sort of instrumental accompaniment.They were also known as "cori spezzati", since the choirs were structured in musically independent or interlocking parts, and may sometimes also have been placed in physically different locations.The concept of allowing two or more concurrently performing choirs to be independent structurally would probably not have arisen had there not been an already existing practice of choral accompaniment in church.