On April 10th 1859, a choral society in Leipzig, the Riedel-Verein, gave the probable premiere of a large-scale composition by Johann Sebastian Bach. Parts of it had been sung and played before but this is thought to have been the first performance of the whole thing, more than a century after Bach's death. The publisher of the first edition had proclaimed it as "the Greatest Work of Art of All Times and All Nations" and many people would agree with that assessment today, but it's still a musical and liturgical enigma. Why did a pious Protestant write a Catholic Mass? Was it meant to be performed all in one go? Catherine Bott explores Johann Sebastian Bach's greatest enigma: his Mass in B minor. Listen to this amazing programme here, thanks to Radio 3.