Barbara Thornton (New Jersey, January 6, 1950 - Cologne, Germany, November 8, 1998) was a singer, musicologist and groundbreaking performer of medieval music. Thornton, described as “one of the most eminent medieval voices of our time” (Neumann 1998), was educated at Sarah Lawrence College, the Conservatorium van Amsterdam, and the Schola Cantorum Basiliensis. In 1977, she founded the ensemble Sequentia with Benjamin Bagby in Basel. They moved to Cologne that same year, where they lived and worked together for 21 years (Neumann 1998; Zahn 2001). Sequentia has released many fine recordings, most of them on Deutsche Harmonia Mundi (Weber 2001). In 1982, the group began to stage Hildegard von Bingen’s Ordo Virtutum, which proved so successful, both in concert and on record, that they undertook to record all of Hildegard’s musical output—a project completed in 1998 for the celebration of the abbess’s 900th birthday (Neumann 1998). The group has also performed music written in the 12th century from the musical centers Santiago de Compostela, Aquitaine, and Notre Dame. Thornton died in Cologne on 8 November 1998 at the age of 48, after having suffered for a number of years from an inoperable brain tumour (Neumann 1999).