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.
Copyrights do not last forever. When copyrights expire, the works are considered part of the public domain. Right now, most works published prior to 1923 are in the public domain while more recent works are covered by copyright. Currently, copyright laws are in effect for 70 years after the death of the creator of the work. So, if an author died in 2080, her books would not enter the public domain until 2150.