Hildegard von Bingen (1098-1179) was a German nun (She was the tenth child in the family; the number ten in the middle ages was considered 'perfect', so she had to be sent to church to become a nun!) She wrote religious poetry set to music. It resembled the Gregorian chant, but was highly original and never drew from existing repertory. She also wrote a morality play "The Play of the virtues". Hildegard compiled a book of liturgical songs entitled "Symphonia armoniae celestium revelationum".
This particular chant however is called "O pastor animarum" (O Shepherd of Souls). The chant had an important part to play in later music, when it was used as the foundation of structures of greater complexity.
Oxford Camerata
Jeremy Summerly
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