"IT IS a truth universally acknowledged," says the American composer Ned Rorem, "that the entire solar system is torn between two aesthetics: French and German. Virtually everything is one or the other. Blue is French, red is German. No' is French, yes' is German. Formal gardens are French, oceans are German. The moon is French, the sun German. Gay men are French, lesbians are German. Crows' feet are French, pigs' knuckles are German. Schubert on his good days is French, Berlioz is forever German. Jokes are French, the explanation of jokes is German. If French' is to be profoundly superficial, like Impressionism, which depicts a fleeting vision of eternity, then German' is to be superficially profound, as when Bruckner's music digs ever deeper into one narrow hole. If you agree with all this, you're French. If you disagree, you're German."

It is a point he makes in his bracing autobiography Knowing When to Stop, published in paperback just a month ago, and it is a point that is wholly Roremian: delightful for its cleverness and spontaneity (very French), but fierce, even leonine, in its claim on truth (one hundred percent German). The fact is that for all Rorem's Americanness, he is both sides of his own equation: a man whose music can be as ethereal as Ravel's and as cerebral as Schoenberg's; a prose writer whose words may strut and flirt across a page, but whose elegiac themes are never far beneath. There is heart, there is brain. Charm and gravity. Savoir vivre and Drang.

Rorem was born in Richmond, Ind., and raised in Chicago -- the only son of liberal, even left-wing Quaker parents. His father was a professor of economics at the University of Chicago and the conceptualizer and founder of Blue Cross. His mother felt keenly about supporting women's suffrage, gay rights and birth control, but confined her opinions to her family and directed her drive and intellect to the raising of her two children. Theirs was not a stodgy home. Socially conscious, educationally upper class, they were "bohemian in the safe style of university denizens." Too Wasp to kiss or hug, they nevertheless "paraded nude" among themselves; and they did it in such a "businesslike" manner that it was a shock to learn that other families did not behave in the same way.

From nursery to high school, Rorem attended Friends' meetings with his parents and older sister, and studied at an experimental school run by the faculty of the University of Chicago. It was a remarkably mixed institution -- largely Jews and blacks -- and he was blind to the differences among his playmates until he left its halls. "Only when I went out into the world did I learn how sexy and interesting those differences really were."

He was given all the music lessons he asked for. By 10 he proclaimed himself a composer. By 13 he was reading Andre Gide, and when his parents took him to France later that year, he fell in love with the country. But his real love affair with France would not flower for another 15 years.

At 16 he graduated from high school and began his studies at Northwestern University's music school, "but I soon felt that I was straining against the faculty. I urgently wanted to learn the music of my time and place -- not the classics." It is a position he has held fast for almost 60 years, and one he speaks on today with almost missionary fervor: "Serious contemporary concert fare has all but vanished during the past 20 years," he says; and it has done so "in the ken of even the most educated laymen. Intellectuals who appreciate' the arts of past and present know their Dante as they know their Dinesen, and adore Praxiteles as they adore Pollock; but when it comes to music they may thrive on Vivaldi or even Mahler but not on these men's living equivalents -- we contemporary composers are not even a despised minority, for to be despised you must exist."

Within two years, he left Northwestern for Philadelphia's Curtis Institute of Music (his father had sent them a sheaf of his compositions). But even in the creative atmosphere of Curtis he felt too constrained by his teachers. Before a year was up, he left Philadelphia, and, against his father's wishes, went to New York to work as Virgil Thomson's manuscript copyist. "I still tend to take music schools with a big grain of salt," he says. "They're good at smelling a rat and pointing out solutions, but they can't make a composer out of someone who isn't."

But Manhattan in the '40s offered a young composer a different kind of schooling: Rorem befriended Aaron Copland, Paul Bowles, John Cage, Eugene Istomin, Billie Holiday. He had his first homosexual affair, learned how to drink, enrolled in Juilliard, took odd jobs as a rehearsal pianist, and was hired and fired by Martha Graham.

By 1949 he was in Paris, fulfilling a long-lived fantasy of submerging himself in that culture. ("I was already French," he wrote.) There he met Truman Capote, Francis Poulenc, Jean Cocteau, James Baldwin, Samuel Barber. He would write about the musical and sexual encounters of that heady time in The Paris Diary (1965), an unprecedentedly honest memoir that would reach cult status in pre-Stonewall days.

Established as a solid, productive writer of music, Rorem went on to publish 11 more books, among them The New York Diary (1967), Critical Affairs (1970), Setting the Tone (1983), The Nantucket Diary (1987)and Settling the Score (1988). Not incidentally, he won the Pulitzer Prize for his "Air Music" in 1976, and is widely acknowledged today as one of America's greatest living composers. Author of hundreds of compositions, from songs to chamber music to full symphonic works, Rorem now lives and works in New York City and Nantucket.

In 1994, he published Knowing When to Stop. Despite its juicy revelations ("I have been in bed with four Time covers: Lenny Bernstein, Tennessee Williams, Noel Coward, and John Cheever"), the book was most notable for its wry and probing reflections on an American life in music.

What Rorem's writing does best is express an angst about the shrinking world of the musical mind. "There was a time," he says, "when the performer and the composer were one and the same: Beethoven, Chopin and Debussy all played their own works. Not so now. My good neighbor {violinist} Itzhak Perlman makes in one night what a composer makes in one and a half years of work." Today the performer is a star; the composer hardly exists. Writing a symphony in the America of the '90s, it seems, does far less for one's pocket or ego than writing a book or painting a canvas.

And then there is the question of American musical confidence: "Americans know they're better than the rest of the world in bombs and budgets, but retain a vague inferiority vis-a-vis the musical arts, still feeling that European repertories, not to mention European conductors, are better than ours."

Well, this is all fearfully serious. Gloomy even. Downright German. Which prompts me to inquire, "So which side of you, Ned Rorem -- the composer or the writer -- is French?"

It stumps him only momentarily. And then he starts in: "Well, if prose is German and music is French -- although subdivisions of prose, like essays, are French, while subdivisions of music, like symphonies, are German; and Schubert, say, though anatomically Austrian, was, in his economy, Frenchish, while Franck, though biologically Belgian was, in his profligacy, Germanic -- then, maybe, according to my own definition. . . ." Here, he stops.

"Wait, let me put on my thinking cap. But which one? I do wear two, but never both at the same time." CAPTION: Ned Rorem