Composed in 1906, the Chamber Symphony op. 9 for 15 solo instruments represents a high point in Schönberg’s artistic development. The reasons that motivated Schönberg as early as 1914 to arrange this Chamber Symphony for orchestra were not only related to practical performance aspects, however (enabling performance at larger concert halls), but were also connected to the fundamental problem that originated quasi-intrinsically from its hybrid position between orchestral and chamber music. The orchestral version from 1914 was never published and is now available for the first time as completely new orchestral material. A later orchestral version, which is further from the original, was produced by Schönberg when he was already in American exile.