The correspondence within Schubert’s close circles of friends comprises private letters exchanged between 1806 and 1830.

Over 80 percent of the letters included in this edition are published for the first time from original manuscripts. Some of these sources are located in publicly accessible collections in Austria and Germany, where complete or partial estates of individuals are preserved. However, many letters remain within numerous family archives in Austria. Furthermore, a large number of further pieces are accessible through libraries, archives, and other private collections internationally. 

In addition to the friendship letters, a smaller amount of intra-family correspondence spanning multiple generations has also been included due to its close ties to the exchange between Schubert’s friends. The correspondence, aside from personal reflections, covers themes mainly within the realms of music history, art history, literary history, theater history, intellectual history, and social history, along with matters related to the convict system in Kremsmünster and Vienna.

Among the most important characters represented in this edition are members of the Bauernfeld, Bruchmann, Hartmann, Kenner, Kupelwieser, Schober, Schubert, Schwind, and Spaun families.