Final answer:
Hildegard of Bingen is the revered composer and contributor to Gregorian Chant, known for her sacred music compositions during the medieval period.
Step-by-step explanation:
The composer and important contributor to Gregorian Chant is Hildegard of Bingen. Gregorian Chant, a form of medieval sacred music, was typically monophonic and part of the liturgical tradition of the Christian church. Hildegard of Bingen, a German Benedictine abbess, was known for her contributions to this genre in the form of numerous compositions and liturgical texts. Though not the inventor of Gregorian Chant, her work within this musical tradition is highly regarded and exemplifies the sacred music of the medieval period.