I'm not aware if he ever did music of a genre of Christian music.
Yes, gospel music is one of many Christian music sub-genres.
I've grown up listening to Gospel music. Sounds interesting, what was the purpose of the gospel music? Was it just for aesthetics, or perhaps religious and ceremonial, or just entertainment? Or would it be a combination of the them? None for me, for my parents and neighbors it was probably for religious and aesthetic reasons as I grew up in the South East. I rather listen to Elvis if you ever heard of him. He's one of the top most regarded cultural icons of the 1900s. One of the typical ways to refer to him is "the King". Exactly, I wonder if he ever did any gospel music.
Gospel music is a genre of Christian music.