VERDI A Life in the Theatre By Charles Osborne Knopf. 360 pp. $22.95

IN 1970 Charles Osborne's The Complete Operas of Verdi, also published by Alfred A. Knopf, promptly became the source of choice for anyone wanting to know how Verdi achieved his incredible list of operas. Osborne, in that volume, not only gives his readers the contents and structures of every opera from the Oberto, Conte di San Bonifacio (1839), to one of the greatest of all comedy operas, Falstaff (1893), he also illuminates, in handsome elegance, the long road that Verdi traveled in those more than 50 years. And along the way, he places in excellent perspective the Requiem, the String Quartet and the Verdi songs, of which there are more than 20.

Even at the time of writing that superb descriptive book, Osborne had seen all 28 Verdi operas, in theaters reaching from Melbourne in his native Australia to Moscow. Today, every one of the operas has been recorded. Twenty-four are listed in current Schwann catalogues, some -- Aida, Rigoletto, La Traviata and Il Trovatore -- in as many as eight, 10 and even 12 different recordings.

In his new book, Osborne places his chief emphasis on Verdi's incredible feeling for the operatic theater -- for what would most powerfully appeal to audiences, what would work best on stages where singing and acting were (Verdi always hoped) accorded equal importance. It is fascinating to read Verdi's insistent directions for the most minute details in the staging of some of his most famous scenes. Osborne quotes Verdi's explicit orders to any soprano taking on the role of Lady Macbeth:

"Anyone who has seen Ristori knows that it must be performed with a minimum of gesture, or rather with one single gesture: that of erasing a blood-stain she imagines to be on her hand. Each movement must be slow, and each step should be barely visible; her feet must steal over the ground, as if she were a statue or a ghost. Her eyes should be glazed, her appearance corpse-like; she is on the point of death and will die immediately afterwards. Ristori emitted a rattle -- a death-rattle. This should not and cannot be done in music, just as there should be no cough in the last act of La traviata . . . " (With such specific directions from Verdi himself, how is it that some sopranos, and their stage directors, continue to allow Violettas to hack and cough their way through that infinitely touching final scene of La Traviata, as if the audience might not realize that the singer is dying of tuberculosis? True, there are many sopranos whose avoirdupois makes it very difficult to believe that they are indeed on the point of death, a factor that added to that famous failure the night of the first performance of the opera.)

On the subject of those who sang in Verdi operas and who sing in them today, Osborne has a brilliant quotation from one of the less happy tenors of Verdi's day, Giuseppe Fancelli, whom Verdi had to accept in the role of Radames at the vitally important premiere of Aida at La Scala (after the world premiere of the opera in Cairo six weeks earlier.) The illness of Giuseppe Capponi, the tenor Verdi preferred, made it necessary to use Fancelli instead. Osborne quotes Verdi's friend and publisher, Giulio Ricordi, concerning one rehearsal:

"Having made Fancelli repeat the same phrase over and over without obtaining any result, Verdi rose to his feet, seized the tenor by the back of his neck, and, while repeatedly pounding the man's forehead on the keyboard, burst out: 'When will anything ever get into your head? Never!' "

Ricordi adds the tenor's astonishing complaint, made to his colleagues, after Verdi's departure: "A great Maestro, yes, sir! I agree. But he wants the impossible! He wants people to read his music as he wrote it, and to sing on pitch and in tempo, and even to pronounce the words! How can you do all that stuff at the same time? I couldn't, even if I were Almighty God himself." For what less, you might well ask, should a composer have to settle?

OSBORNE's subtitle, "A Life in the Theatre," is nowhere more apt than in his giving in full Verdi's outline for the opera he for many years longed to write, but never did, King Lear, from that source that gave him three of his greatest works -- Macbeth, Otello and Falstaff -- his beloved dramatist, Shakespeare. In 1850, not long before the sensational arrival of Rigoletto, Il Trovatore, and La Traviata, Verdi wrote his friend and sometime librettist, Salvatore Cammarano, not only stressing the desirability of an opera on Lear, but giving a detailed outline of the opera as he saw it, in four acts and 11 scenes, an outline that makes you long even more for the opera Verdi could never write.

Among the less well-known, but significant aspects of Verdi's creative life that Osborne continually makes clear, are the psychosomatic illnesses that so often beset the composer while he was in the midst of composing.

While Osborne keeps his principal emphasis on Verdi, the man of the theater, his new book gives welcome attention to the generous, loving side of the genius, his family and friends, his courage in surviving sorrow -- the death of both of his daughters and his wife within a period of two years -- his intense patriotism in the years when Italy was struggling to become a united nation and, finally, his unquestioned rank as the finest Italian composer of the entire 19th century. The book is a delight and a treasure.

Paul Hume, former music critic of The Washington Post, is a radio commentator on WGMS and author of biographies of Ignace Jan Paderewski, John McCormack, and Verdi.