BOOK REVIEW / NONFICTION : Master of the Radio Broadcast Stands Out on Paper, Too : NORMAN CORWIN’S LETTERS <i> Edited by A.J. Langguth</i> ; Barricade Books $29.95, 467 pages

Norman Corwin is probably best known as the dean of the radio dramatists of the so-called Golden Age, a man who understood how to use the medium of broadcasting to create a veritable symphony of human voices.

But, as we discover in “Norman Corwin’s Letters,” Corwin’s radio scripts are not his only handiwork. He has written poems, plays, essays and books; he composes word puzzles and off-color limericks. Above all, Corwin was (and is) a prodigious and often passionate letter-writer whose personal archives contain some 10,000 letters, a vast collection of correspondence that amounts to eyewitness testimony to a half-decade of American politics and culture.

So lively is Corwin’s mind, so probing his curiosity, that Corwin’s correspondence amounts to a spotlight that sweeps across the historical landscape and pauses now and then to illuminate some intriguing sight. As we read through these hundreds of letters, long and short, we see him pause on a poem by Robert Frost, an encounter with a future victim of the Stalinist purges, a scene from the Six-Day War, and a sojourn in South Africa.

The first cut from Corwin’s vast collection of letters was made by Corwin himself. A.J. (Jack) Langguth, an accomplished journalist, historian and biographer, made the final selection. The result is an intriguing work of history and biography in the form of highly intimate correspondence that spans more than 60 years.

The recipients of Corwin’s letters, whose names are prominently displayed on the dust jacket, include many luminaries of American popular culture, ranging from Bette Davis and Groucho Marx to Leonard Bernstein and Orson Welles. A good many, however, are addressed to Corwin’s various relatives--and we are given only Corwin’s side of the correspondence.

The very first letter in the book is a sentimental note to his parents on the occasion of their 25th wedding anniversary: “Be mindful, on this day, that the best is yet to be! “ writes the young Corwin with the pluck and good cheer that characterizes his personality and his politics.

Corwin reports on his health, his love life, his finances, even the bargains that he has found: “Just now bought a new silent Corona portable, which retails for $67.50, for $54.67.” He offers up a bit of doggerel, including a flirtatious little poem to the actress Dorothy Maguire: “Not even I/Can understand why/A girl so ostensibly shy/Should wear, in full view of the public eye,/A dress with an open fly.”

His otherwise high spirits tend to flag in the ‘50s, when so many of his colleagues in the media fell under the cloud of McCarthyism. Corwin is not merely gallant but downright courageous in offering work to Judy Holliday when she fell afoul of the blacklist: “I am distressed to hear that the goons are still at it,” he wrote. “Even the Christian martyrs had a chance to kick a lion in the nose before being clawed by the mighty paws.”

The letters tend toward chattiness and intimacy, especially when he is writing to his family. Only rarely does Corwin work himself up to the certain grandeur of language that is reminiscent of his radio scripts:

“And because Wisdom is a rare radium,” he wrote in one letter, praising the company of the night before, “buried under tons of shale and clay and disintegrating granite, it is wonderful to pass through a triple concentration of its rays all in one evening.”

More often, though, a wry and sometimes sly sense of humor pervades Corwin’s correspondence, as when he banters with his editor at Simon & Schuster about the sexual allure of mountain goats: “Once, in a moment of passion, I cried out to a shapely Angora, ‘Tell me you love me!’ ” Corwin joked. “Not a twitch from her.”

His earliest letters show Corwin to be a born showman with a hunger for praise and applause, and yet he was also an earnest teacher who believed that he had something of value to say to the public. When he was still a young newspaper reporter, he described a speech that he had given at a local high school--and he specified exactly how long the clapping lasted.

“My formula was merely to give them something they could understand, appreciate and find amusing,” he wrote at the age of 24, neatly summing up a credo that has lasted a lifetime.

Toward the end of “Norman Corwin’s Letters,” we see that Corwin--who has outlived many of his colleagues and contemporaries--is tending to write what can only be described as fan letters. (Indeed, he wrote a great many such letters to various editors and reporters for The Times.) But even his most casual notes ring with Corwin’s endearing charm and verve.

“There could be no greater symmetry between two people unless they were twins,” Corwin wrote to Ray Bradbury in 1988, “or were named Yo Yo Ma and Yo Yo Pa.’

And yet, if Corwin is sometimes sentimental and even corny, the collected letters confirm that Corwin is what Langguth calls “an honest liberal.” They also show how Corwin’s stubborn belief in humankind’s better nature survived even the worst excesses of his century.

“Corwin has celebrated a country he found splendid in its idealism and valor,” Langguth concludes. “We know that Norman Corwin’s America exists because Jefferson, Lincoln, Thoreau and Whitman have lived there before him.”

The last letter in “Norman Corwin’s Letters” is dated only six months ago, and we must assume that Corwin, a vigorous 85, is still writing. But Langguth reports that Corwin has abandoned his own efforts at autobiography, and so “Norman Corwin’s Letters” will have to serve as the definitive account of his life. Happily, it does.