When Bach composed them, in his last years in Köthen, those pivotal years that were to lead him to Leipzig, he already had an incredible number of masterpieces behind him. He took the trouble to make a beautiful fair copy of this work. It's a product of his maturity. But since these pieces serve as a basic tool for learning the piano, they're inevitably overshadowed by the larger cycles, like The Well-Tempered Clavier, the Goldberg Variations, The Art of Fugue and so on. But that's a mistake, because there's an extraordinary density of music in the Inventions and Sinfonias. Zhu Xiao-Mei.