 Further, we have no knowledge of the keys and orchestration which Bach used.While the libretto specifies which chorale melodies were used, Bach's harmonizations remain uncertain.According to Bach Digital, the Passion was scored for SATB singers, two traversos, two oboes, two oboes d'amore, a string section consisting of two violin parts and two viola parts, organ and continuo, possibly complemented by two violas da gamba and two lutes.