I just watched “White Gospel” on the iplayer and it is worth watching. Its the story of the music that inspired lots of artists which came out of churches in the south. Starting with “Sacred Harp” music (which certainly isn’t exculsively white), which is an incredible form of religious music. Basically, the song leader stands in the middle of the church, surrounded on 4 sides by the congregation who arrange themselves according to their singing parts (treble, alto, tenor, bass). There is a lot of “Fa Sol La Mi” singing, and obviously a lot of biblical content too. The singer’s belt out the words, and a lot of them chop their hands down in the air to keep rhythm.
So, this religious music led to smaller groups of 4 singers touring America to help spread new hymns and songs (funded by the music publishers) eventually these groups became popular in their own right. One of the most successful were the Blackwood Brothers, who after a tragic plane crash, lost two singers, and employed a new bassist called JD Sumner, who was reputed to have the deepest singing voice in the world. JD went on to to start the “JD Singers” who became Elvis’ gospel backing group.