Four generations of composers (born between 1824 and 1928) whose work became influential after 1905 are the subject of this vast survey of modern music. Collaer explains that bridging the gap from earlier music to the contemporary period is analogous to passing from Euclidean to non-Euclidean geometry. If modern music appears decadent, he says, ""it is due only to the public's difficulty in distinguishing the various trends"". Collaer's principal concern is the way in which recent developments have penetrated musical language. Composers, he believes, search the musical vocabulary for ideas upon which to exercise their own creativity. Despite the natural absence of historical perspective from this ""history"", the book is a rewarding one, rich in penetrating biographical material on all the important figures of the era. Several pages are devoted to a chronological list of all known composers of the period and virtually all their works. Among the highly personal vignettes are scattered dispassionate opinions on a number of controversial issues such as electronic music, writers (not composers) whom he describes as ""captive of a metallic frenzy"". A rank amateur will probably find Collaer's scope a bit beyond him, but sincere listeners with just a bit of background stand to profit greatly. The reference value of this volume will doubtless endure beyond the popularity of some of the subjects.