The new six-volume “Oxford History of Western Music” was 13 years in the making. Despite its bulk, it may seem to pale in comparison with, say, the 29-volume second edition of The New Grove Dictionary of Music and Musicians, of 2001, but that represented the work of more than 2,500 writers. This is the work of one, Richard Taruskin, a music historian at the University of California at Berkeley, who has been an occasional contributor to Arts & Leisure and other publications.