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.
This field is for noting the date the edition associated with the listed ISBN was published. Date published can most usually be found on the copyright page of a book. That page will tell you when the work was copyrighted - and if the book is a first edition, the copyright date will be the same as the date published. If it is a later edition, the date will be different. Some books, not all, will list dates for subsequent publications somewhere on the copyright page.