Bach composed Two Part Inventions in Köthen (before 1723) for teaching purposes, particularly his eldest son Wilhelm Friedemann. The earliest copy of this work, supposedly written by Bach's own hand, is found in the Wilhelm Friedemann Clavierbüchlein (Piano Notebook), started on January 22 1720. The Notebook contained two-part pieces, Preambulum, which were later named as Inventions. In Bach's copy of 1723 he prefaced the collection of Inventions and Sinfonias with these words: "Honest method, by which the amateurs of the keyboard - especially, however, those desirous of learning - are shown a clear way not only to learn to play cleanly in two parts, but also, after further progress, to handle three obligate parts correctly and well; and along with this not only to obtain good inventions (ideas) but to develop the same well; above all, however, to achieve a cantabile style in playing and at the same time acquire a strong foretaste of composition." For Intermediate students, amateurs and professionals.