Modern classical music is music written in the 20th century and beyond. Although much of it draws heavily on earlier forms, modern composers also experimented with rejection of long-held ideas; notably, Arnold Schoenberg questioned the traditional notions of harmony with his twelve-tone system[?], and John Cage questioned the very definition of music with his use of chance and found sounds.
... (1853)
Die Poesie and ihre Geschichte (1885)
Studien (1839-47)
Neue Studien (1875-78).
He published also an autobiography entitled Von Magdeburg nach Königsberg ...