Few literary projects have been pursued by Adorno as long and intensely as his Beethoven project, but none got stuck in a comparably early stage of work. According to his own statements, he has been projecting a "philosophical work on Beethoven" since 1937, with the oldest surviving records dating from the spring or summer of 1938, shortly after Adorno's move to New York. After the end of the war and his return to Frankfurt am Main, only notes and records were kept, which then nearly abruptly ceased in 1956. In the essay on the Missa solemnis, which he included in the anthology "Moments musicaux" in 1964, he writes about his "long-conceived Beethoven book": "So far, it has not been written down, primarily because the author's efforts have repeatedly faltered at the Missa Solemnis." Until the very end, it has "not been written down.".