Debussy wanted to distance himself from what he considered the emotional excess of the Romantics and instead wanted to write music that, through sound, created an ambience similar to that of the Impressionist painters and Symbolist poets of his day.
All books initially copyrighted in the US from 1964 through 1977 have had their copyrights automatically renewed (by law) and the copyrights are still in force. The initial copyright term was 28 years; the renewal was for 67 more years.
Taking a work in the public domain and modifying it in a significant way creates a new copyright on the resulting work. For instance, the Homecoming Saga by Orson Scott Card is a re-telling of the Book of Mormon. Therefore, the books in the Homecoming series can be copyrighted.