Religion in the music system
Spirituality in Jazz
Duke Ellington
NPR story. Read the article and listen to the audio.
John Coltrane
Sun Ra
Sun Ra: From Ephrata (F-Ra-Ta) to Arkestra by David W. Stowe
Jazzmen: Diz and Sun Ra by Amiri Baraka
Mary Lou Williams
Mary Lou Williams' website. Browse as much as possible, including all of [1]