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.
Books with LCCNs of a different year than the year in which they appear occur frequently and do not imply that the book is old. A book that took a lot of planning and research may be 2-3 years in the making and, therefore, may have a 2001 LCCN with a 2002, 2003 or 2004 publication/copyright date. This doesn't mean that the material is old to anyone but an uninformed sales guru.