Bach’s work catalogue, Wolfgang Schmieder’s famous Bach-Werke-Verzeichnis (BWV), will have to be extended by an additional number. In late March 2008, the two musicologists Stephan Blaut and Michael Pacholke from Halle University discovered a hitherto unknown organ composition by Johann Sebastian Bach (1685–1750) among recent acquisitions of the Universitäts- und Landesbibliothek Sachsen-Anhalt in Halle. The work is a large-scale fantasia based on the chorale “Wo Gott der Herr nicht bei uns hält”. The current edition of the Bach-Werke-Verzeichnis records only the first few bars of the piece in its appendix (BWV Anh. II no. 71), failing to cite any source.
Now a complete copy of the work came to light among the papers of the former Thomaskantor and renowned editor of Bach’s works Wilhelm Rust (1822–1892); Rust had copied the composition in 1877 from a now-lost manuscript formerly located in Königsberg (now Kaliningrad). The provenance of this lost source can be traced back to the immediate circle of the composer. The exceptional quality of the composition leaves no doubt as to its author. The chorale fantasia comprises 85 bars and was written between 1705 and 1710.
(Hans-Joachim Schulze, translation by Stephanie Wollny)