Yet he says that at least an attempt at such summary must be made if Tippett's oeuvre is to be put into perspective. He takes a bold leap, and concludes that the common element in many of the major works produced in the last quarter century (for examples, he cites such stylistically and esthetically disparate pieces as Stockhausen's 'Kontakte,' 'Momente' and 'Stimmung,' Ligeti's 'Atmospheres,' Boulez's 'Pli selon pli,' Berio's 'Sinfonia,' Henze's 'Essay on Pigs' and Maxwell Davies' 'Eight Songs for a Mad King') is that the music 'comes down heavily in favor of the humanistic.'

One wishes he'd explored the theme in depth: There is much to be said about the genuinely 'humanistic' music of our own time, and a concise essay on the subject by a writer of Kemp's caliber would doubtless aid listeners in separating the material that really matters from the plethora of modern compositions in the so- called neo-Romantic vein that purport to deal with humanistic concerns but in fact are merely expressive, in an old-fashioned way, of basic human emotions. But Kemp quickly passes over the substantial avant-garde music he says 'represents a kind of ecological crusade against the technological, a celebration of man's rediscovered faith in himself.'

His main subject, after all, is the music of Tippett, an artist whose relationship with 'this movement of sensibility,' he says, 'is not so unequivocal as that of the composers referred to above.'

The implication is not that Tippett pulled his punches when addressing humanistic issues. Rather, Tippett's music has always been concerned with man's role in a changing world. Whereas Stockhausen, Ligeti and the others in the 1960s deliberately changed their tune, so to speak, in order to communicate certain newly embraced humanistic attitudes, Tippett in the same period simply continued along the same path he'd been following for several decades. At least in terms of its humanistic content, there are no easily identified turning points in Tippett's music. Tippett's work is all of a piece, Kemp suggests, and it is only because the underlying philosophy is so consistent that its relevance to specific social or political issues perhaps seems ambiguous.

Publication of Kemp's 516-page 'Tippett: The Composer and His Music' (Da Capo Press; $37.50) coincides with the worldwide celebration of Tippett's 80th birthday on Jan. 2.

In terms of biographical facts, there's little here that has not already been at least sketched in Kemp's own article on Tippett in the 'New Grove Dictionary of Music and Musicians,' in David Matthews' 1980 'Michael Tippett: An Introductory Study' (Faber and Faber) or in the monograph that Meirion Bowen, Tippett's longtime friend and traveling companion, produced in 1982 for Robson Books' 'The Contemporary Composers' series. But the examination of specific pieces is much more thorough than anything else that's appeared in print thus far. Interwoven with the detailed musical analyses is a wealth of tangential commentary speculating on the psychological motivation behind certain works and adventurously measureing Tippett's achievement against that of his contemporaries. The book must have gone to press early, for it does not deal at all with 'The Mask of Time,' a two-hour oratorio that had its world premiere in Boston in April of last year, and which Tippett himself has said can be regarded as the culmination of a half century of thinking about music. That serious omission aside, it's a commendable study, a richly informed and highly informative appreciation of England's foremost living composer.

SOME OF THE MOST penetrating insights are to be found in Kemp's discussions of the changes of direction Tippett took in the late 1930s and in the early 1970s.

The first was prompted by disillusionment with socialism, a political movement to which Tippett was passionately committed for a decade after his graduation from the Royal Collegeof Music in London.

After several months of Jungian therapy, Tippett realized that 'he could now rededicate himself to his fundamental vocation of composer and set aside his involvement in politics, or at least in party politics,' Kemp writes in the introductory section of the book. 'From his analysis, he drew not only an understanding of the private and general forces which had prompted his dreams but an emotional and intellectual balance which left him better equipped artistically. The price to be paid for his new confidence was a feeling . . . of being alone. This did not mean that he was denied serious friendships with other people; but it did mean that he resisted the temptation to recapture the profound emotional experiences he had recently undergone because he knew that such experiences were both transient and certain to throw his life out of balance.'

To be sure, balance -- between purely musical elements, between music and text, between musical form and expressive content -- is something that Tippett has sought in all the music he's written since 1940.

Whether he always achieved it is debatable -- his catalogue includes pieces such as the 1941 oratorio 'A Child of Our Time,' in which the powerful anti-war rhetoric of the composer's own libretto effectively overwhelms the work's conservative and fairly predictable musical ideas, as well as pieces such as the 1945 Symphony No. 1 and the 1963 Concerto for Orchestra, in which the extremely facile handling of abstract musical material seems to outweigh expressive force and emotional substance.

But with his 1970 opera 'The Knot Garden,' Tippett's gradually developing style -- by this time intense, eclectic and rich in extramusical imagery -- finally came into line with the humanistic thinking that s urfaced even in his student works.

'ALL TIPPETT's music is direct in expression, in that it is as lucid and immediate as is compatible with the nature of its subject,' Kemp writes in his chapter on this second crucial turning point in the composer's career. 'But the directness of 'The Knot Garden' and its successors is unlike that in his previous music. It is stripped, defenseless, importunate. It lays the emphasis on publicizing rather than 'poeticizing.' It speaks of a composer whose earlier convictionshad been placed under serious threat and who now needed to rethink and reassert them with maximum forcefulness in order to make himself heard amid the general clamor of dissenting voices. To harness the power of music to expressive honesty may involve thedisturbing and the violent. It may also invite charges of self-indulgence. If this is the case, Tippett seems to be saying, so be it: The matter is too urgent to be compromised by deference to to over-refined sensibilities.'

Kemp says that with 'The Knot Garden' Tippett entered 'the expressionist phase' in his output. The later music has much in common with the angular melodic lines, brutal dissonances and disjunct rhythms of early- 20th-century German Expressionism, he says. But 'its terms of reference are wider,' and 'it neither wages war against a hostile world nor presumes that music can embrace the abstract essence of things by means of an 'absolute' metaphor.'

In the theatrical works of this still current 'Expressionist' period ('The Knot Garden' and the 1976 opera 'The Ice Break'), the subject matter is the interior lives of the characters, and the light Tippett sheds on the deeper recesses of the psyche is so illuminating it's almost frightening. The purely instrumental works (most notably the third and fourth symphonies, from 1972 and 1977, respectively, the 1978 String Quartet No. 4 and the 1979 Triple Concerto for violin, viola and cello) are similarly probing, but here the focus is more general: The extra-musical theme is nothing less than theineffable essence of the human being, and almost always the structure of the piece somehow alludes to the on-going cycle of life, death and re-birth.

In 1974 Tippett updated the slim volume of transcripts of radio talks he'd published 15 years earlier under the title 'Moving Into Aquarius.' One of the new essays was called 'Poets in a Barren Age,' and in it the composer offered an explanation of sorts for his life's work:

'I have been writing music for 40 years. During those years there have been huge and world-shattering events in which I have been inevitably caught up. Whether society has felt music valuable or needful, I have gone on writing because I must.

'And I know that my true function within a society which embraces all of us is to continue an age-old tradition, fundamental to our civilization, which goes back into pre-history and will go forward into the unknown future. This tradition is to create images from the depths of the imagination and to give them form whether visual, intellectual or musical. For it is only through images that the inner world communicates at all. Images of the past, shapes of the future. Images of vigor for a decadent period, images of calm for one too violent. Images of reconciliation for worlds torn by division. And in an age of mediocrity and shattered dreams, images of abounding, generous, exuberant beauty.'