Bach’s cantatas form an inexhaustibly rich corpus of the highest musical inspiration, embracing all the compositional tendencies of his time and thus of his own music. The two masterpieces coupled here invite us to measure his evolution over a decade. In Weimar, with the Cantata BWV 21, we see him in a period of experimentation, turning to the model of Buxtehude to express a vivid pietism. In Leipzig, with the Cantata BWV 76, we sense the mastery of a composer using all his resources in a vertiginous synthesis to the glory of God.