BWV 639 is one of J.S. Bach's most famous organ works.
Less known is an extended version of this BWV chorale
prelude Anh. 73. It was probably written by Bach's son
Carl Philipp Emanuel. He mainly used the original
composition and added some elements to it. But maybe
it's an original J.S. Composition by Bach, as Bach
often reworked his compositions... Although it is not
obvious since the added elements are more written in
the gallant style, characteristic of C.P.E. Bach's
compositions.
