The chorale prelude to “Erhalt uns Herr bei deinem Wort”, BWV Anh. II 50 sounds to me like it could have been composed by Bach. Other examples of this type of chorale prelude (manualiter, three voices) can easily be fond in the oeuvre of Bach. But then again, the same is true for Johann Gottfried Walther, for example, or numerous other composers in northern germany. Whether or not by Bach, the piece itself is of high quality and is a pleasure to play. It is a two voice fugue with the theme based on the first phrase of the chorale melody. The chorale melody it set against this fugue, as the soprano voice. Try it for yourself.
HW: Principal 8′, Rohrflöt 8′, Nassat 3′
Score available here: partitura.org/index.php/johann-sebastian-bach-erhalt-uns-herr-bei-deinem-wort-bwv-anh-ii-50/