Ensemble Organum is a group performing early music, co-founded in 1982 by Marcel Pérès and is based in France. Its members have changed, but have included at one time or another, Josep Cabré, Josep Benet, Gérard Lesne, Antoine Sicot, Malcolm Bothwell. They have often collaborated with Lycourgos Angelopoulos and are influenced by Orthodox music.   The group mainly focuses on the performance of music from the Middle Ages, including Beneventan, Old Roman, Gallican, Carolingian and Mozarabic chants. However, the repertoire includes renaissance polyphony as well as more recent works.   The ensemble was formerly based at Sénanque Abbey and Royaumont Abbey. Since 2001 it has shared facilities in the precinct of Moissac Abbey with the Centre itinérant de recherche sur les musiques anciennes (Centre for Itinerant Research of Medieval and Early Music). In addition to musical performance, the ensemble also works with musicologists and historians on musical research from this period.