Present-day Christian religious bodies known for conducting their worship services without musical accompaniment include some Presbyterian churches devoted to the regulative principle of worship, Old Regular Baptists, Primitive Baptists, Plymouth Brethren, Churches of Christ, the Old German Baptist Brethren, Doukhobors the Byzantine Rite and the Amish, Old Order Mennonites and Conservative Mennonites. What is the name of the religious a cappella style used with shape notes?