Wednesday's celebration of Irving Berlin's 100th birthday began at the stroke of midnight with four dozen fans softly serenading the composer of many of America's most beloved songs with "I'll Be Loving You Always."

"He says to say, `Thank you.' He's very grateful to you all," a woman called down from a fifth-floor verandah of Berlin's home on Manhattan's East Side, where Berlin listened from his window.

"He came to the window and looked out, but said it was too cold to come out," explained a young fan named Geraldine. "We're sorry we couldn't bring him out."

One ruddy man clutching a 40-year-old photograph of Berlin - then already 60 - shouted: "At least let him come to the window!"

"Happy 100th birthday, Mr. Berlin!" another cheered up into the cool spring air.

The midnight serenade was the first celebration Wednesday marking the centennial of the composer of some of the nation's most beloved songs.

Wednesday night, he was to be honored at a gala Carnegie Hall concert sponsored by the American Society of Composers, Authors and Publishers, of which he is a charter member, and Carnegie Hall.

He wrote his first hit song in 1911, "Alexander's Ragtime Band," and by the time he was 24, he had written for the Ziegfeld Follies, had earned $100,000 in Tin Pan Alley royalities and was on his way to becoming a living legend of Broadway and Hollywood.

The scores and songs - some 3,000 in all - are among the nation's best loved tunes. They include "God Bless America," "I'll Be Loving You Always," "White Christmas," "Easter Parade," "A Pretty Girl is Like a Melody," "I Love a Piano," "Cheek to Cheek," "This is the Army, Mr. Jones," "They Say Falling in Love is Wonderful," and Broadway's anthem, "There's No Business Like Show Business."