This woman wrote a book relating her religious visions. The song is written as a late medieval plainchant in a form called a sequence...a series of short tunes sun twice with a slight variation. (AA', BB', CC'.....N). The soloist sings A and then the choir sings A' and so on. There is a continuous drone running in the background...the combination produces a serene, yet intense feeling of spirituality. (Reminds me of the drone in "Hey Joni")
Hildegard Von Bringen - "Columbia Aspexit"