This study is about the contribution of Franz Hauser to the rediscovery of Johann Sebastian Bach and his works in the nineteenth century. Originally from Bohemia, Hauser was an opera singer, voice teacher, and researcher. He systematically collected Bach’s compositions and created a catalogue – the first scholarly annotated list of works of an important composer. The most complete version was destroyed during World War II. However Hauser’s partial lists of Bach’s works provide important, authentic information useful for example in cases of disputed authorship. Hauser was an unusually avid collector of Bach’s compositions, using a network of contacts all over Germany, and other collectors considered him an expert and authority.