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.
Since copyright law began to emerge, society has changed in more ways than authorship. The printing press may have made more text available in the late seventeenth and eighteenth centuries, but technology in the form of computers and the internet have made texts even more widely available.