The Interpretation of Cosmic & Mystical Experiences, by Robert Crookall, was first published in 1969 and has been intermittently available since via various booksellers (e.g., Amazon.com). The book is available through interlibrary loan from various libraries, but finding a circulating copy becomes more difficult with each passing year. Fortunately, it appears that Google Books has a complete digital version of the book.
The Music Man tried to explain how he was orchestrating the original score, but he used compositional terminology that was frankly way over our heads, so we will simply quote from the email.
Hope You Enjoy the Music and the Book Trailer,
P.S. If you'd like to hear all of the Music Man's orchestration and arrangement of Du Fay's composition, click above. Music should play. Isn't technology wonderful when it works?