George Gershwin: This Rhapsody's For You There May Not Be Complete Harmony Yet About This American Original. But In His 100th-anniversary Year, The Music Can Be Heard Everywhere.

Alow clarinet trill opens Rhapsody in Blue.

What follows, that upward clarinet run, specifically notated but transformed by an improvising jazz player into a gliding, exultant cry, turned classical music on its ear. It introduced George Gershwin as the man who would forever confound those who want to separate music into discrete, labeled boxes.

The clarinet that opens Rhapsody in Blue hurls into the air this century's most widely recognized and instantly identified American work. It also kicked up controversy that continues to this day about the composer's capabilities, his seriousness, his ``suitability'' as an emblem of modern American music.

None of this controversy has abated, even as a world enlivened by Gershwin's music celebrates the composer's centenary on Saturday. Almost 60 years after his death, Gershwin's music is heard everywhere. Airliners lift off with Rhapsody in Blue pumping through earphones. No cabaret singer can exist without the songs; pianists make careers from the two pieces with orchestra; opera houses worldwide profit from the crowds wanting to hear Porgy and Bess again.

Few composers who have created so few ``serious'' works have so dominated a musical era. Gershwin's catalog of orchestral music comprises Rhapsody in Blue and Concerto in F, two small tone poems, An American in Paris and Cuban Overture, Variations on ``I Got Rhythm'' and Second Rhapsody. His opera, Porgy and Bess, was preceded by a short piece, Blue Monday. Piano pieces and a violin work and some juvenilia complete the list.

Critic Peter Yates noted a generation ago that Gershwin's ``inner conflict'' pitted his enormous talent against an equal reluctance to attempt large-scale, serious work. The view now is that Gershwin knew his strengths, kept to song forms and used his gift for melody to sustain every piece over 32 bars in length.

He was a songwriter, so full of melody and song ideas that he could afford to throw away what did not take shape quickly or fit his assignment. He was an improviser whose fingers drew boundless melodies from the keyboard and then cloaked them in harmonies iconoclasts hadn't even imagined.