Following Horkheimer's taking up the directorship of the Institute, a new journal, "Zeitschrift für Sozialforschung", was produced to publish the research of Institute members both before and after its relocation to the United States. Though Adorno was not an Institute member, the journal published many of his essays, including "The Social Situation of Music" (1932), "On Jazz" (1936), "On the Fetish-Character in Music and the Regression of Listening" (1938) and "Fragments on Wagner" (1938). In his new role as social theorist, Adorno's philosophical analysis of cultural phenomena heavily relied on the language of historical materialism, as concepts like reification, false consciousness and ideology came to play an ever more prominent role in his work. At the same time, however, and owing to both the presence of another prominent sociologist at the Institute, Karl Mannheim, as well as the methodological problem posed by treating objects—like "musical material"—as ciphers of social contradictions, Adorno was compelled to abandon any notion of "value-free" sociology in favour of a form of ideology critique that held on to an idea of truth. Before his emigration in autumn 1934, Adorno began work on a "Singspiel" based on Mark Twain's "The Adventures of Tom Sawyer" titled "The Treasure of Indian Joe", which he never completed; by the time he fled Hitler's Germany Adorno had already written over 100 opera or concert reviews and 50 critiques of music composition.