Over the past few years, music lovers have been rearranging their furniture to make space for stack upon stack of back issues of The New Yorker--so as to be able to keep Andrew Porter's weekly review-essays within easy reach. Well, now Porter's deserved legions of admirers can throw out those magazines and make room instead for this grand and joyous compilation. In his introduction, the English-bred critic pinpoints the special nature of these reviews: they are ""part descriptive chronicle, part essay in which a particular performance may be viewed as the latest addition to the long history of a work."" Thus, Porter's interest is ""usually in the work itself. . . . Hence the emphasis on accuracy and integrity of editions, on aptness of instruments, acoustics, and performing style. . . ."" And so, unlike most reviews, these will never date: when Porter covers Verdi at the Met, he has vivid, concerned, witty comments on the current soprano, but, more important, he gives you the opera in deep perspective--not just what it was that night, but what it has been in the past and could be next year. This sort of erudite criticism/scholarship might, under another baton, be long-windedly pedantic. With Porter conducting, however, the enthusiasm, common sense, and sheer humanism make these crisply written explorations infectious as well as educational; even casual fans will find themselves caring intensely about details previously unnoticed in blurs of sound. The contents? Over 100 musical events, 1974-1977, and not just in New York. Lots of opera, with as much emphasis on the 20th-century and opera in English as on Porter's Italian specialties. Plus that definitive treatise on audience behavior (""At the Right Time, In the Right Place"") and--typically conscientious--cross-references to books and disks so that the learning process can go on and on. Music of Three Seasons, then, is indispensable on three counts--as the liveliest record of serious musical life in America in the mid-1970s; as the richest music criticism of our time; and as some of the most elegant and thoughtful and unselfish criticism of any time, of any kind.