Irving Berlin is so American he makes apple pie look almost "un." Despite a quarter century out of the public eye, the composer of "God Bless America," "White Christmas," "Blue Skies" and hundreds more remains alive in the public ear.

And in the syncopated beating of the public heart. If America were a show, the credits would say, "Words and music by Irving Berlin."An all-star concert of Berliniana-- taped Wednesday on Berlin's 100th birthday, at Carnegie Hall --will be seen May 27 on CBS. But tributes to Irving Berlin are perpetual. His songs have become folklore, vernacular, as familiar and comfortable as everyday conversation.

What special qualitites do Berlin's songs have? "Elusive, I think," says Bobby Short, the greatest cabaret singer. "His work is not witty, really, but it is very down-to-earth. And amazingly natural."

"The main thing about Berlin is that he inspired a lot of envy in all other composers," says Mark Sandrich Jr., a composer himself and the son of the director of "Top Hat," "Carefree" and "Follow the Fleet," classic Astaire-Rogers musicals with Berlin scores.

"It all seemed to come so easy, as if he never had to work at it--though of course he did," Sandrich says. "His songs didn't have any seams. They didn't feel like anybody every wrote them. It was more like Berlin just walked down the street and plucked them out of the air."

Berlin, says Sandrich, was very insecure about the quality of his work, even after he'd become a legend. A self-taught craftsman who couldn't read music, who grew up in poverty after coming to the United States from Russia in 1892, Berlin imagined he wasn't in the same class as giants like Jerome Kern, the Gershwins, and Rodgers and Hart.

In 1954, when Berlin emerged from one of several semi-retirements to write new songs for the movie "White Christmas," he said "I thought I was finished. I thought I'd had it as a songwriter, but I was just tired. I had spells of great depression, and the only thing that could get me out of it was going back to work."

In his recently published history of the show-business Friars Club, "B.S., I love you," Milton Berle remembers Friars afternoons that brought together George M. Cohan, Enrico Caruso, Gentleman Jim Corbett, Al Jolson-- and Irving Berlin. John Philip Sousa would be there, too.

Attempts by the outside world to reach Berlin in recent years have mostly proved futile. He did participate in a Berlin spectacular staged by Ed Sullivan on CBS in the '60s. For his 1973 book "They're playing our Song," Berlin talked briefly on the phone with author Max Wilk.

"You're wasting your time," Berlin told Wilk right off. "Who cares anymore? There's a whole new public out there, and they don't even know people like me are still around. We're museum pieces. Today, it's all kids."

Those kids write songs to express their innermost feelings. Berlin wrote his songs hoping to please not himself, but the public. His songs expressed our innermost feelings. Remember?

"Remember we found a lonely spot

and after I learned to care a lot

you promised that you'd forget me not

But you forgot to remember."

How long will the world sing the songs of Irving Berlin? Not for just an hour, not for just a day, not for just a year, but always.