The prelude of this work is a beautifull, Mendelsohn-like, piece. It is not unlike the third part of Mendelsohn's fourth Sonata, even if that piece is in F major and this one in a minor. The left hand plays a choral like melody, while the right hand provides a two part accompaniment. It is a beautifull, bittersweet piece. The fugue is based on a modulating theme that leads to a very chromatic piece, iwthout it being too obvious. All in all a nice example of Richter's craftmanship in counterpoint and composition.
Update: not only "choral-like", it ís the melody of a choral. Eric (Hoofdwerk) pointed out it is in fact the melody of "Warum betrübst du dich, mein Herz". Hence the mood of the piece. One cannot but admire the subtle way in which Richter expresses the chorale in his music.
I played the prelude a bit faster than the first time I recorded it: http://www.contrebombarde.com/concerthall/music/32814
. Not intentionally, it just came out like this. Obviously a piece, thati s very susceptibel to one's own mood while playing.
Score available here: http://partitura.org/index.php/ernst-friedrich-richter-praludium-und-fuge-a-moll