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.
The following section looks at each of these routes into the public domain more closely. Copyright has expired for all works published in the United States before 1923. In other words, if the work was published in the U.S. before January 1, 1923, you are free to use it in the U.S. without permission.