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.
Thousands of works published in the United States before 1964 fell into the public domain because the copyright was not renewed in time under the law in effect then. If a work was first published before 1964, the owner had to file a renewal with the Copyright Office during the 28th year after publication.