Most of Darr's works were not published in his lifetime, which makes dating his music almost impossible. Many manuscripts and most of the printed music is preserved at the Bavarian State Library (Fritz Walter and Gabriele Wiedemann Collection).
Many of Darr's compositions remained unpublished throughout his life, complicating efforts to determine their dates. The majority of his manuscripts and printed works are kept in the Bavarian State Library (Fritz Walter and Gabriele Wiedemann Collection).