 Following the French "Association Laws" against religious congregations passed by Minister Waldeck-Rousseau, Dom Pothier moved from France to Belgium with his exiled community in 1901.A musicologist, disciple and collaborator of Dom Prosper Guéranger, Dom Pothier contributed to the reconstitution, the restoration and the renewal of the Gregorian chant, a form of monophonic, unaccompanied sacred song of the Roman Catholic Church.Besides being the composer of many Gregorian songs ("Officium Defunctorum", 1887) and the writer of a huge number of articles, Dom Pothier was also the head and editor of the "Revue du Chant Grégorien" (1892–1914) - supervising the publication of several works (Hymnes, Christmas office, Antifonario, Cantus mariales) -, the founder of the "Paléographie Musicale" publication for the dissemination of medieval liturgical manuscripts, and the author of a new edition of the choir books based on manuscripts of the Gregorian chant and of several studies on the plainchant, including "Les mélodies grégoriennes d'après la tradition" (Gregorian Melodies According to the Tradition), 1880, his chief work which became the standard work on the subject.