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.
Works also fall into the public domain once the copyright in a work expires. Works published in the United States prior to 1923 are not covered by copyright and exist in the public domain. Works published after 1923 through 1978 are protected by copyright for 95 years from the publication date.