Clavier-Übung II is a collection of harpsichord works by Johann Sebastian Bach.
The reason for the transposition is not known: one speculation is that the aim was to increase the contrast between the two works.
Another possible motivation is that out of the eight German note names A, B (B♭), C, D, E, F, G, H (B♮), six had already been used as keynotes in the Partitas, thus only F and H remained.
[2] The sequence continues into Clavier-Übung II with the Italian Concerto, a seventh down (E to F), and the French Ouverture, an augmented fourth up (F to B-natural).
Thus the sequence of customary tonalities for 18th-century keyboard compositions is complete, extending from the first letter of his name (Bach's "home" key, B♭, in German is B) to the last letter of his name (B♮ in German is H).