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.
A book published by a US author in the US, with copyright notice and renewal after 1922 and before 1978 would be copyrighted for 95 years. After that it would most likely be 95 years unless the author was independent (not employed as an author), in which case it would last 70 years after the year of the author's death.