Johann Sebastian Bach wrote the Two-part Inventions as excercises for his students. The text that Bach himself added to his 15 Two-part Inventions translates as:

"A faithful Guide, whereby admirers of the Clavichord are shown a plain Method of learning not only to play clean in two Parts, but likewise in further Progress to manage three obbligato Parts well and correctly, and at the same time not merely how to get good Inventions, but also how to develop the same well; but above all, to obtain a cantabile Style of playing, and together with this to get a strong Foretaste of Composition."

Level 2 of this piece is considerably easier to play than the original version.