Kirchhoff seems to have elvated the ciaconna to his trademark technique for writing a choral prelude. His prelude to the famous melody of "Ach Herr mich armen Sünder" has a theme of eight bars in the bass voice that is repeated nine times in a row. Above the repeating theme the choral melody is played in the soprano voice with right hand, with an accompaniment for the left hand (aided by the right hand, in places where the choral melody is not playing).
It is quite an accomplishment to have a repeating bass voice set against a choral melody. A choral melody often migrates through several modes or keys, in this case a minor, C major and e phrygian. The bass line has to be constructed to accommodate those different keys or modes, and be logical and musical in itself. In this case Kirchhoff succeeds very well in that difficult task.
In the lass 8 bars Kirchhoff notates only figured bass. The first eight bars of this prelude can serve as a realisation for this figured bass and the score I created reflects this possibility.
I performed this composition twice. Once on the sampleset of of the Klapmeyer organ in the St. Nikolai church in Altenbruch and once on the sample set of the Schittger organ in the St. Martini-kerk, Groningen he first one is a relatively small church with a short reverbaration. The second one is a larger church with a reverbaration of about 6 seconds.
The two different spaces create their own different sound and of course the two organs are vastly different as well. Even though it is the same composition, it sounds very different on both organs, almost like different pieces. Which one do you prefer?
Score availabele here: http://partitura.org/index.php/gottfried-kirchhoff-ach-herr-mich-armen-sunder/