Johann Sebastian Bach

Johann Sebastian Bach (1685-1750) published his Duetto (4) in 1739 at the end of his third book of Clavier-Übung (Keyboard Practice), his monumental compilation of works for the harpsichord. In essence, the Duetto are two part inventions but with more elaborate forms than most of the other works Bach called Two Part Inventions. The Duetto No. 4 in A minor, BWV 805, is the most complex of the four with the most convoluted theme and the most elaborate developments. The theme itself is long and highly chromatic, presenting plenty of opportunities for modulation. The theme is stated first by the left hand alone and then in the right hand with detailed counterpoints in the left hand. The first episode starts in the minor with the opening of the theme, then it moves to the major with the close of the theme. The third statement of the theme is once again in the left hand, but this time with counterpoints in the right hand and the fourth statement is once again in the right hand, but with new counterpoints in the left hand. The second episode starts with fragments of the theme in both hands and builds to a shattering climax followed by a transition based on the opening of the theme. The fifth statement of the theme is in the right hand with counterpoints in the left and the sixth statement is in the left hand with new counterpoints in the right hand. The third and final episode fragments both halves of the theme in both hands and builds to the seventh and final return of the theme in both hands, leading to a big final cadence.

-- AllMusic.com