Bach composed his 15 Two-Part Inventions or as he called them Sinfonias for Keyboard at the same time as their 15 Three-Part Counterparts. They are designed to as Bach himself says: 'To play cleanly in two voices...(and) deal correctly with three obbligato voices...but above all else to acquire a true cantabile style of playing and with it to get a good foretaste of the art of composition'.