You may have heard that Michael Cretu didn't want the public to know who created Enigma. That's why he's credited as "Curly M.C." on the first Enigma album. Ironically, Sacred Spirit's producer Claus Zundel has come much nearer to achieving truly enigmatic obscurity, despite platinum record sales and multiple Grammy nominations. Googling his name (or his alias, "The Brave") yields sparse results, and I cannot find any kind of home page for Sacred Spirit or B-Tribe (Zundel's other major project).
Morpheus Music hosts the most definitive discography I can find, but I still have unanswered questions. An Amazon search confirms the existence of Sacred Spirit Volumes 1, 2, 8, and 9. Do Indigo Spirit, Classical Spirit and Moroccan Spirit represent some of the missing volumes? There are listings for Volume 3 on both the German and Japanese Amazon sites, but the Japanese listing has no picture or track listing, and the German version is listed as a Japanese import with the same cover art as Volume 2. Assuming all these are members of the series, there is still one Volume that is completely unaccounted for.
Since Zundel has provided no clear way to organize his work, I'm making my own judgment call, and including anything with the word "Spirit" in its title here. B-Tribe will eventually have a separate page.