Definition and background:
Early liturgical music of southern Italy, perhaps predating Gregorian chant. It contains texts and melodies from the 7th century Roman rite, but was in use between the 10th and 13th centuries.
For more information on the music term "Beneventian rite" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary