Wer nur den lieben Gott lässt walten

Johann Christoph Kühnau (1735 – 1805) was a German composer and conductor. He was born in Volkstädt, near Eisleben. He received his musical training early in live from a town musician in Ascherleben. In 1763 he became teacher at the Realschule in Berlin, in 1788 at the Dreifaltigkeitsschule and in 1788 he became Kantor at the Dreifaltigkeitskirche in Berlin.
He was mostly known as editor of a hymnal for part-singing, but he edited contemporary organ music as well. The chorale prelude on “Wer nur den lieben Gott lässt walten” comes from his edition “Choral Vorspiele für das Orgel und das Klavier”.
It is undoubtely based on a chorale prelude on the same melody by Johann Philipp Kirnberger: Kühnau adds a right hand part where in Kirnbergers piece the left hand plays solo. And save for a few adaptions in the chorale melody almost all the notes of Kirnberger’s piece are in Kühnau’s piece as well. Perhaps this adaptation was meant as a tribute to Kirnberger, who had high praise for Kühnau’s hymnal.

Kirnberger's version is here: http://www.contrebombarde.com/concerthall/music/17205

Score available here:
http://partitura.org/index.php/johann-christoph-kuhnau-wer-nur-den-lieben-gott-lasst-walten/