The one musician that I find spiritual in an interesting manner is Albert Ayler. From his song titles, to the manner of his playing, which has a "witnessing" type of quality, he seems to make many explicit connections with spirituality. I'm listening to him a lot right now, and I find Live at Slug's Saloon vol. 1 & 2 to be deeply spiritual, having a very "Gospel Choir" approach in the playing.
P.S: For a download of Ayler's most famous spiritual moment, THIS LINK will let you download part of his playing at Coltrane's funeral (it's the first one on the top). Be warned -- the sound quality is not very good, if fact, it's crap!