Hildegard von Bingen was a medieval woman of accomplishments. Given to a monastery early in childhood by her nobility parents, she devoted her life (1098-1179) to the Church and to creative endeavors. Besides founding and supervising (in succession) a couple of abbeys near her hometown of Bingen on the Rhine, she wrote prodigiously: letters, poems, illuminated manuscripts, and liturgical chants. Her literary output, now the subject of extensive scholarly attention in Germany though not yet in this country, reveals her to have been a devout mystic with claims to holy visions, a fesity advocate of church reform, a strict disciplinarian of exact moral standards, and a ready dispenser of medical sex advice. Her musical compositions, as local composer and organist Frank Ferko has discovered, show a highly inventive mind: the 70 or so chants were unusual for the 12th century in their extremely high vocal (coloratura) ranges, mixing of musical modes, and the complex yet sensible notational system. So impressed is Ferko that he's written a large-scaled, one-hour-long organ piece using as thematic materials five of Hildegard's chant melodies. Titled Hildegard-Zyklus, it consists of ten contrasty movements--each inspired by one of the abbess's vivid descriptions of her visions of the activities of God. The work will be performed for the first time this Sunday on the newly-installed organ at St. Alphonsus Church. Ferko, who holds a doctorate in music from Northwestern, has won recognition primarily for his choral music; and one can detect in his recent works a strong affinity for the French tradition--especially the music of Messiaen and Poulenc. Sunday, 4 PM; St. Alphonsus Church, 1429 W. Wellington; 878-3101.