J. C. Bach’s Symphonies and the Breitkopf Thematic Catalogue

The importance of the Breitkopf thematic catalogue ¹ to musicologists in questions of authenticity and chronology has long been acknowledged. Not only is this by far the largest thematic catalogue of its kind and time, but it also gives, in addition to the incipit, other important information about each registered work: name of composer, instrumentation, beginning of text, and in many cases also opus number, publisher's ² home town, and composer's appointment. That Johann Gottlob Immanuel Breitkopf, the publisher of the catalogue, was fully aware of the importance, perhaps even the historical significance, of these catalogues is clearly shown by his famous "Nacherinnerung" on pp. 29–32 of the "Parte Ima" from 1762, in which the fact that the works are made known through their "Themata" ³ is stressed and in which the problem of authen 226ticity, which has been so crucial to 20th century musicologists and bibliographers, is discussed.