The church of the monastery of Santa Maria de Bellpuig de les Avellanes had an organ at least since the 18th century. The old instrument was installed in 1747 by the community of Premonstrate canons. In 1845, following the confiscation of Mendiz'bal, the monks were expelled and the organ was subsequently auctioned and installed in the church of Maldà (Urgell), where it was probably destroyed during the Spanish Civil War.

After 170 years, the church of the Monastery of Les Avellanes recovered the sound of the organ, thanks to the Marist Brothers community. The organ installed is not new; it was built in 1967 by the Schwenkedel house (which disappeared in 1974) and comes from the Marist Community of Varennes-sur-Alier (France), which, after 140 years of religious life, closed its doors. Before doing so, however, he decided to donate the instrument to the Monastery of Les Avellanes.

It is an organ with 845 tubes, neo-baroque aesthetics. It was purchased through the military pensions of the young French Marist brothers who fought as fighters in World War I. The commission for its transfer and assembly was carried out by the Catalan company “Organum BCN”. The community of the Monastery of le sAvellanes and the Town Hall of Os de Balaguer have committed to publicizing this new musical heritage, promoted concerts. For this reason, since 2015, they have been participating in the "Orgues de Ponent and the Pyrenees Autumn Music Festival", which is organized every year.