Erbarm dich mein o Herre Gott (LV 28)

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.
Both themes occur 16 times in the piece, Though from the manuscript it is not immediately apparent. The final entry of the second theme is rather hidden in the way the scribe notes the final bars. He writes two a's and c'as tied quarter notes. So I first played that as a half note a-c chord.

However, after I had played the piece several times, I realised it was not meant as a chord but the tenor voice plays c - a and the alto voice plays a - c, effectively creating two consecutive quarter note a-c chords.
I decided to make it clear in my score that the tenor voice actually plays a final entry of the second theme.

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 fingerings, 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.

Score available here: http://partitura.org/index.php/riedrich-wilhelm-zachow-erbarm-dich-mein-o-herre-gott-lv-28/