The philological project "The Music Library of Maximilian Franz" is intended to identify and establish provenance of the surviving music-dramatic sources that originally belonged to Maximilian Franz (1756-1801), the youngest son of Habsburg Empress Maria Theresa and the last Elector of Cologne, as well as to analyze these sources to answer detailed questions about performance practices at his court in Bonn. Max Franz is known to music history primarily in two capacities, as an admirer of Wolfgang Amadeus Mozart and the first employer of Ludwig van Beethoven. It is the second of these that the proposed study should most benefit, as the period when the musical life in Bonn was most vibrant, from 1780-1794, directly corresponds with the composer's formative years. However, the benefits would extend beyond Beethoven studies, since a more detailed portrait of musical life at this court would also provide greater understanding of practices at smaller German courts in general. Additionally, both the geographical proximity of Bonn to important musical centers of Paris, Berlin, and Mannheim, as well as the political ties to Vienna, make it an ideal case study for the cultural transfer or histoire croisée which is often believed to have marked the internationalization of the musical style during this era. We are currently in a better position than ever to deepen our knowledge of the musical practices in Max Franz's electoral court. Previous research by scholars such as Sieghard Brandenburg and Juliane Riepe have located several of the sources in Modena, but a detailed study of these sources has been thus far lacking. Such a study is long overdue: this period ranks as one of the greatest biographical lacunae in Beethoven studies, and therefore a more precise picture of the musical life in Bonn would form a necessary first step for a modern re-appraisal of his earliest musical experiences. Beyond this, Max Franz's court was also home to a number of outstanding musicians, whose biographies would also benefit from the results of this study: among others, Christian Gottlob Neefe, Andrea Lucchesi, Nicholas Simrock, and Anton Reicha. The first phase of this project shall be directed at systematically identifying the Modena sources and making the results public in a clear presentation of their extent and nature in form of an open access database. This step being completed, the second phase aims to address broader questions of operatic performance practice at Max Franz's court, including, among others, an analysis of the musical capacity of the Bonn Hofkapelle, information on the praxis of arrangement at the Bonn court or substitution arias, or the question of in which language the operas were performed. It is also hoped that the first stage will make it possible to identify further sources scattered throughout Europe, e.g. in Vienna or among the estate of Christian Gottlob Neefe..