Billy Joel has a rock and roll soul and a classical heart. He began taking piano lessons at age 4 after his parents noticed his fondness for Schubert's romantic melodies. He borrowed a melody in his song ''This Night'' from Beethoven's ''Pathetique'' sonata. He siphoned Aaron Copland's Western zest in ''The Ballad of Billy The Kid,'' his orchestrated rock rodeo of 19th and 20th Century bandits.

In 2001, Joel completed an eight-year experiment by releasing ''Fantasies & Delusions,'' a CD of his solo classical pieces steeped in Chopin, Debussy and Rachmaninoff. It was recorded by Richard Joo, who has better classical chops than Joel, in Mozart Hall in Vienna, the hometown of Joel's half-brother, who is a symphonic conductor.

On Saturday night, Joel will receive his classical diploma during the 151st anniversary concert and ball at the Academy of Music, Philadelphia's most hallowed hall. First the Philadelphia Orchestra, the academy's former tenant and current owner, will perform a new orchestration of his ''Waltz No. 2 (Steinway Hall),'' which premiered on ''Fantasies & Delusions.'' Then he'll perform arrangements of his songs, including '''Nylon Curtain' Suite'' and '''Uptown Girl' Variations,'' with his band and the orchestra. It will be his first live gig with a major orchestra in a five-decade career.

The 58 year-old will enhance his reputation as a philanthropist by jump-starting the orchestra's Billy Joel Endowment Fund for Education. After decades of raising money for everything from the Amazon rain forest to bay men on his native Long Island, he's recently become a major musical humanitarian. In 2005 he gave six-figure donations to seven Eastern music institutions. Last month his new song, ''Christmas In Fallujah,'' began funding Homes for Our Troops, which helps customize residences for wounded soldiers.

The performance will take place in a city that's showered Joel with brotherly love. In 1972 he became a minor celebrity after WMMR-FM, the Philadelphia rock radio station, recorded and released a live version of ''Captain Jack,'' his gritty saga of suburban angst. Kept in rotation for a year and a half, the recording led him to sign with Columbia Records, the powerhouse label for Bob Dylan and Simon & Garfunkel. Adopted as a hometown hero, Joel's popularity is memorialized in a Wachovia Center banner marking his 46 Philly sell-outs.

Joel, a crossover musician, will share a crossover bill on Saturday, 151 years to the day of the academy's very first performance. The orchestra will perform an etude for PVC pipes with Blue Man Group, three mute, kinetic, inventively percussive men in blue make-up. Former caterers Matt Goldman, Phil Stanton and Chris Wink spray spectators with everything from food to paint and satirize everything from information overload to egotistical rock stars.

Soprano Disella Larusdottir will sing Donizetti and Puccini arias. The Iceland native won the vocal award in the orchestra's 2007 Greenfield Competition for greater Philadelphia students. Past honorees include pianist Andre Watts and violinist Nadja Salerno-Sonnenberg.

Conrad Tao, a 13 year-old pianist, will excerpt Rachmaninoff's ''Rhapsody On A Theme of Paganini.'' In 2006 he wowed Lehigh Valley listeners by soloing on Mozart piano and violin concertos with the Pennsylvania Sinfonia Orchestra, then encoring with one of his own works.

The gala is a keyboard bonanza. Joel wrote ''Baby Grand'' as a duet for himself and fellow pianist Ray Charles. Christoph Eschenbach, the Philadelphia Orchestra's music director, debuted with the ensemble in 1973 as a pianist. Blue Man Group's battery of percussion instruments includes a stripped piano placed on its side, tuned to one note and hammered on the strings by a large soft mallet.

Saturday's event has two primary purposes, according to academy president Joanna McNeil Lewis, who grew up on the Philadelphia Orchestra's famous children's concerts. Proceeds will help restore and preserve the academy building, including its 5,000-pound chandelier, by itself a $1.4 million project. The National Historic Landmark and America's oldest continuously used opera house has outdoor gas lamps, an interior modeled after that of La Scala in Milan and a fabled musical legacy. This is where the Philadelphia Orchestra gave the first American performance of Gounod's ''Faust,'' where Gustav Mahler conducted his eighth symphony with more than 1,000 performers, where Frank Sinatra entertained World War II soldiers in a basement canteen.

The concert/ball will also raise the academy's profile as an all-purpose cultural center. For 151 years, it has presented ballets and Broadway musicals, reunions of Civil War generals and Supreme Court justices, high-school graduations and technological commencements. In 1877 Alexander Graham Bell transmitted live music from New York to Philadelphia to demonstrate the revolutionary telephone.

The academy's public-relations campaign began in earnest last year, when it switched the gala from a primarily classical program to more of a variety show. The Philadelphia Orchestra honored Leopold Stokowski, its legendary music director from 1912 to 1940, by accompanying the Disney movie ''Fantasia,'' which he helped create, conduct and orchestrate. Offscreen Eschenbach mimicked shaking hands with Mickey Mouse, which ''Stokie'' did onscreen.

As Lewis points out, last year's gala revived the splashy spirit of the first gala. That 1957 event featured performances by three musical hall of famers: pianist Artur Rubinstein, violinist Isaac Stern and singer Dinah Shore. Eugene Ormandy, the Philadelphia Orchestra's music director, shared conducting chores with Danny Kaye, an appropriate assignment for a comic actor who played Walter Mitty, James Thurber's dramatic dreamer.

This year's edition is designed to please more generations. Joel unites young and old through his songs ''Just The Way You Are,'' a wedding favorite for its lovely melody and feisty message, and ''We Didn't Start The Fire,'' a classroom favorite for its catchy summary of 20th-century history. Tao and Larusdottir represent the up-and-coming musicians whose careers Joel is financing and the Philadelphia Orchestra is grooming.

Even the oddest act doesn't seem so odd. Blue Man Group, after all, is equally an avant-garde and family act. Blue men who act like resident aliens aren't that weird, says Lewis, in a building that once hosted an indoor football game on a wooden field.

The event will also mark the launch of the Philadelphia Orchestra's Billy Joel Endowment Fund for Education, which will be dedicated to improving classical music education in the Philadelphia area.

Billy Joel has been a supporter of Homes for Our Troops for several years. Around Christmas, Billy Joel sent his annual donation on behalf of close friends to the national non-profit organization that provides specially adapted homes for our severely injured troops. This year, the donation was substantially larger.

Lots of listeners no doubt attend the Academy of Music's anniversary concerts because they love the old hall and because they love the Philadelphia Orchestra in it.

In recent years, though, the gala concert has become less old-society-centric and more of an event whose tickets go in blocks to corporations sponsoring the event. Audiences may marvel at the Academy's elegance, as last night's white-tie and gowned crowd no doubt did at the 51st iteration of the event.

But orchestral music? For many younger attendees, it's like crashing a party and finding everyone else is speaking a different language.

So last night Billy Joel was brought in to translate. Even if the pop-music figure reached his musical apex in the 1970s, this crowd seemed happy to relive its high school and college soundtrack. The Academy's aim of involving a younger crowd in the 151-year-old building's future seems to have worked, at least for a night.

You needed no further proof than the 16 measures Joel turned over to the audience in a fast waltz called "Piano Man." The audience knew every word.

This pop-infused follow-up to last year's anniversary fete (whose celebrity gilding was provided by Prince Charles, the Duchess of Cornwall, and Rod Stewart) was unusually lucrative. The event and the fund-raising season leading up to it grossed $5.4 million, including Joel's donation of his fee to establish a music education fund at the orchestra in his name. That sum will benefit the orchestra and ongoing restoration of the Academy.

But the whole evening was hardly pop, and not even all of Joel's contribution. Joel is one of those commercial artists who, for reasons hard to explain, have turned to classical. The orchestra played the "world premiere" of an orchestration of Joel's "Waltz No. 2 (Steinway Hall), Op. 5," previously heard as a piano work on a 2001 disc called "Fantasies & Delusions."

The obvious question about a pop star's utterance in classical - does it work as a classical composition? - turns out to be several questions. Yes, it's classical, and, yes, it works. With David Hayes on the podium and an orchestration by Brad Ellis and Joel, it came across as pleasant and well-crafted. But like the other works on Fantasies & Delusions, its borrowings from Chopin and Tchaikovsky are so heavy that they are distracting. Joel could have a future tracing Kandinskys. But so could a lot of people. It doesn't make them artists.

Joel did deliver a thoroughly engaged 44-minute set of the material that proved his originality over three decades. The voice might not be as pitch-secure and strong as it once was. But even now, it's hard not to be moved by his sincere, rhythmically charged anthems and intensely warm stage presence.

The evening was hosted by MSNBC's Chris Matthews, a Philadelphia native, and benefited enormously from the merry prank of a piece called Etude for PVC Pipes and Orchestra, led by Hayes and performed by Blue Man Group, three guys who might be the funniest thing with no voice since Harpo Marx.

And, yes, there was straight classical, with the Philadelphia Orchestra led by music director Christoph Eschenbach, even if there wasn't a lot of it. Two young musicians - soprano Dísella Làrusdóttir and pianist Conrad Tao - made impressions of great promise that only made you want to hear more.