He composes only on the black keys - F sharp - on a piano with a special lever to move into any key.

He has written both words and music to America's most lasting, most loved songs, staring 71 years ago with "Marie from Sunny Italy," for which he earned 37 cents. He once named his eight personal favorites as "Alexander's Ragtime Band," "I Love a Piano," "Always," "Say it With Music," "A Pretty Girls is Like a Melody," "Easter Parade," "White Christmas" and "God Bless America," which made millions of dollars. Profits of "God Bless America" he turned over to the Boy Scouts and Girls Scouts of America when he wrote it for Kate Smith in 1940. It has brought in more than $600,000.

He is co-owner of one of the world's loveliest playhouse, New York's Music Box, which, when it opened in 1921, had the wiseacres predicting he'd never recover the cost. It became known as "45th Street's house of hits," and 57 years later it still is selling out with "Deathtrap."

He was born in Siberla, where his rabbi father and his mother were determined to move their children from the anti-Jewish pogroms. He has had all the honors - from Congress and presidents - his adopted country can prevail on hom to accept.

He is small, natty, painfully shy and intensely romantic.

He will be 90 years old on Thursday and his name, of course, is Irving Berlin.

Mr. Berlin - and that's how his associates always have spoken of him and still do - is much missed by his neighbors in New York's Beekman Place area because they used to relish seeing him, walk his dog and pass the time of day: "Good afternoon, Mr. Berlin." In this tony neighborhood they like to point out this house.

Romantic, this little man? Yes. In 1912, his wife Dorothy, sister of songwriter-producer E. Ray Goetz, died of typhoid fever within a few months of their return from a Cuban honeymoon. Until then Berlin's songs had been humorous or pure rhythm, but putting his grief into his song, he created his first ballad, "When I Lost You." His unique tone of restrained sentiment would filter through many more: "Blue Skies," "All Alone," "What'll I Do?" "Remember?" and "The Song Is Ended."

That last song scared him. It was composed 15 years after Dorothy's death, and just after his second marriage - one on one thought could last, although Irving and Ellin Berlin celebrated their 52nd wedding anniversary in January. Inspiration seemed to desert him after "The Song Is Ended," but when Rudy Vallee aired his neglacted "How Deep is the Ocean?" the spark returned, and Berlin composed a dozen sparklers for "As Thousands Cheer."

He was 40, Ellin 19, the daughter of telegraph tycoon Clarence H. Mackay. They were complete opposites, introduced at a party. Though Mackay sent Ellin to Europe to lure her into other worlds, she refused to forget the composer her father viewed as an upstart.

After their City Hall marriage and even after the birth of the first of two daughters and the loss of their only son, Clarence H. Mackay would have nothing to do with the Berlins. Only after the crash of '29 did he break. As with many a Berlin song, there was a happy ending: The shattered rich man grew to have high regard for his son-in-law. There is a story that Berlin helped his father-in-law financially but since the crash had been rough on him, too, the story may be apocryphal.

One thing about Berlin is not apocryphal: No one ever has gone on the record with an unkind word about him. He was admired from the start, and, at age 24, was a co-founder of ASCAP, the American Society of Composers, Authors and Publishers, with such older peers as Victor Herbert and Jerome Kern. All the in crowd - and, later, Gershwin and Cole Porter - considered themselves his inferiors. Kern once said: "Berlin is American music."

Though President and Mrs. Ford asked him to the White House two years ago to receive the Medal of Freedom, the nation's highest civilian award, he begged off.

Berlin's reticence has not discouraged biographers, though David Ewen's book of nearly 30 years ago is based on the public record. Five years ago an English writer, Michael Freedland, published a 500-page volume without a face-to-face meeting, though they had chatted on the phone.

Affable with the press at informal, happenstance meetings, Berlin increaingly avoided formal question sessions - though on prearranged phone calls he can be direct and obliging

Aware of his lack of education - he was a singing waiter at 14 on New York's Lower East Side - he has an uncommon respect for words. "Watch your lyrics," he once advised young songwriters. "They must say something, tell a story, convey an idea, carry a message. Catchy tunes don't make a song hit."

Of popular songs, he once wrote:

Born to live for a short space of time,

Often without any reason or rhyme,

Hated by highbrows who call it a crime,

Loved by the masses who buy it.

Still though you die after having your sway,

To be forgotten the very next day,

A rose lives and dies the very same way,

Let that be your consolation.

Berlin recently admitted that he has many unpublished songs "lying around" and since he's always been a compulsive worker, they're bound to include some gems. Surely they come out one day.

Until then, why not revivals? Jones Beach this summer will have a Class-A production of "Annie Get Your Gun."

Why not a revival of "Miss Liberty," which could have been so right for the Bicentennial? Its stirring score includes "Gives Me Your Tired, Your Poor," "The Honorable Profession of the Fourth Estate," "Only for Americans" and "The Pulitzer Prize," lyrics fresh and witty in a story about Ellis Island.

Why not a look at that '30s revue inspired by the headlines, "As Thousands Cheer," with topics about presidents, royalty, religious thinkers of East and West, unmarried couples, the Metropolitan Opera and that hauntingly staged "Easter Parade?"

Why not a revue of Berlin words and music? From "Oh, How I Hate to Get Up in the Morning" and "I Want to Go Back to Michigan" (introduced by, of all people, Beatrice Lillie), it could go on to "White Christmas," "Blue Skies," "Harlem on My Mind" and "No Business Like Show Business."

Why not a Kennedy Center special at the start of Berlin's 10th decade?

Of all America's songwriters, he remains peerless. So, happy birthday, Mr. Berlin, even though you think "having birthdays is damn boring." Thanks for the rare words and melodies and the promise of more to come.