In 1955, Berthier was asked to compose music for the Taizé Community, which at the time was only a monastic community of twenty brothers. Six years later, he became organist at the Jesuit church in Paris, Saint-Ignace, where he worked until his death. In 1975, Berthier was again asked to compose for Taizé, this time for the growing number of young people who met there for prayer and worship. For almost twenty years, Berthier composed very understandable church music, and his songs are sung all over the world.
He died in 1994 at his home in Paris.