Focus of his dissertation of Günter Stummvoll is the music practic of two members of the comital family of Harrach: Aloys Thomas Raimund (1669–1742), and his youngest son, Ferdinand Bonaventura [II.] (1708–1778). Over the centuries, the Counts of Harrach played a significant role within the Habsburg Empire. Aloys Thomas held positions of an imperial envoy (kaiserlicher Gesandter) in Dresden, Madrid, Berlin, and Hannover, was Landmarschall of Lower Austria and viceroy of Naples from 1728 to 1733. His son followed in the position of Landmarschall, represented Maria Theresia on the congress of Breda/Nederlands and was governor of Lombardy. During their traveling for diplomatic reasons to different European cities, they collected vast amounts of art. Besides a painting collection, now displayed at Rohrau Castle in Lower Austria, they gathered approx. 400 pieces of music that has been partly sold and is now stored in different locations: The majority is based at the New York Public Library/USA (NYPL), another big part in the Austrian State Archive (OeSta). However, another small part survived in the library of Rohrau Castle, the dynasty’s ancestral seat. Only a fraction of the 400 works is identified. This project aims at identifying and reconstructing the cultural network and transfer processes, for painting an updated picture on the musical practice of a grand noble Austrian family in the 18th century. This will be achieved by using biographical and prosopographic archive research (the family’s economic as well as private archive are held at OeSta) as well as codicological analysis and identification of the music resources. Those music resources are considered as the most important ones of the whole source material. In addition, there is a tremendous amount of archive material (journals, travelling reports, account and financial books, etc.). The given composers (e.g. Ziani, Leo, Porpora, Sarri, Vinci), their places of impact (Dresden, Naples, Paris, Vienna), and major genres (works for Lute, Recorder concertos, opera arias, cantatas) show, that there is a complex of historic and geographic disparate musical listening, playing and collecting practice hidden behind the music collection Harrach, who’s depth, specifics, and socio-cultural dimensions are yet to be fathomed.