The historian Richard Taruskin, author of the Oxford History of Western Music, wrote about Bach: "His [church] music was a medium of truth, not beauty. And the truth he served was bitter … Bach aimed to torture the ear … he could write music that for sheer, deliberate ugliness has perhaps been approached – by Mahler, possibly, at times – but never equaled." Many disagreed with his opinion, however I think there is some truth in it, especially when it comes to pieces where the subject is quite unpleasant, as in the hymn 'Christus der uns selig macht'. The complete hymn text, probably known by many because of the chorale setting in Bach's Johannes Passion:
Christus, der uns selig macht,
kein Bös hat begangen,
der ward für uns in der Nacht,
als ein Dieb gefangen,
geführt für gottlose Leut,
und fälschlich verklaget,
verlacht, verhöhnt und verspeit,
wie denn die Schrift saget.
(translation:
https://www.cpdl.org/wiki/index.php/Christus,_der_uns_selig_macht)
This text explains the many dissonances in this piece. Bach fully explores the drama of the text in this chorale prelude on the hymn 'Christus der uns selig macht' of the Orgelbüchlein. Of course, there are many ways to interprete this piece. Usually I play it slower with a softer registration, but the text above inspired me to go for a different approach; with a firm plenum and a present reed sound for the c.f. (canon) in the pedal, which adds to the drama. Well, I bet there are many different opinions about this piece, the registration and tempo, as usual with Bach. So I can assure you, I will play it differently next year.