Bach Cantata BWV 51 is something of an anomaly. Only boy sopranos were allowed to sing in the Thomaskirche services in Leipzig. The work is too virtuosic for any child singer. One must assume that the cantata was written for some private function in which a female soprano, perhaps Anna Magdalena Bach, sang. The work opens with a bravura aria for soprano trumpet and strings. The soprano and trumpet duetting is of the most brilliant sort, challenging both singer and instrumentalist to the utmost. The very quiet recitative with strings is a complete contrast to the noisy opening. It sets up the beautiful and inward aria with cello. organ and soprano. Here the gorgeous cantalena and plastic phrasing demand a different kind of virtuosity from the singer. Two solo violins swing into a jaunty and irresistible duet that accompanies the singer in her performance of a verse from the chorale "Nun lob, mein Seel." This leads directly into the brilliant Alleluia that ends the cantata.