Kauffmann's prelude to "Warum betrübst du dich, mein Herz" is a slow paced three part piece. Kauffmann prescribes both Cornet and Sesquialetra for the choral melody. Obviously he wanted to make sure it stands out well from the other two voices.
The recording was done with the Hauptwerk software and the sampleset, made by Voxus, of the Müller organ in the Sint Bavokerk, Haarlem (http://www.voxusorgans.com/en/product/haarlem).
Score available here: http://partitura.org/index.php/georg-friedrich-kauffmann-warum-betrubst-du-dich-mein-herz