Translator’s note Dom Jean Claire of the Abbey of Saint-Pierre de Solesmes was for many years engaged in a study of modality in Gregorian chant and in other surviving repertories of liturgical chant of the Latin West. He had perhaps an unparalleled knowledge of the chant, derived from both practice and study. Dom Claire sang the chant at Solesmes from the time he entered the monastery in 1944, and from 1971 to 1996 he was the choirmaster of the abbey and editor of Paléographie musicale, directing the abbey’s long tradition of scholarly and practical publications.