The choral preludes “Erbarm dich mein, o Herre Gott”, LV 28), shows Zachow mastered counterpoint to a high level. The manuscript subtitles this composition as “Choral con Fuga et contrasubjecto”. Though it’s not a fugue in the true sence, the accompaniment of the choral melody is build on two different themes. In order of first appeareance, let’s call them theme A:
and theme B:
These two theme’s occur as stated above and in several variations. Perhaps even the first entry of the alto voice can be considered a variation of theme B. Theme A occurs 16 times in the piece, Theme B occurs 16 times as well. Though from the manuscript it is not immediately apparent. Almost at the end of the piece, the manuscript reads:
Because of the tied notes I first thought half notes a and c were meant. However, after I had played the piece several times, I realised the tenor voice actually has the 16th entry of theme B (see the red arrows in the figure above). The scribe of the manuscript (possibly Gottfried Kirchhoff) perhaps did not realise this, or perhaps he did, yet thought regardless they should be played as tied notes. I decided to make it clear in my score that the tenor voice actually plays a final entry of theme B. To emphasize theme B in those last bars one could consider leaving out the a of the alto voice. The a is already played by the bass voice, so harmonically nothing would go wrong.
On a technical note:
I often show the score in the video in the form of the finished, published text. This time, I thought it would perhaps be nice to show the copy I play from. Playing the music I typeset, is a form of proofreading, so this copy contains indications of the transription errors I made initially. And it contains some finerings, articulation indications and warnings for myself to play the correct duration or the correct note (“A!”). The challenge is of course to spot all occurences of both themes without looking in the score. Though to make it easy, I marked the entries in the video.
The recording was done with the sampleset, made by Sonus Paradisi, of the Schittger organ in the St. Martini-kerk, Groningen.