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.
Under the U.S. laws in effect at the time, the term of copyright for this book was 28 years with the possibility of extending for an additional 28 years. On July 7, 1952, Major General Sweeney, by then retired, renewed his copyright. Thereby his exclusive rights to his work were extended to January 1, 1981.