The Philadelphia Orchestra's intensive Leonard Bernstein Festival provides a wonderful opportunity to follow some of the threads that run through the fabric of my father's music.

The first two pieces in the Festival, Bernstein's Symphonies 1 (Jeremiah) and 3 (Kaddish), tell us much about his lifelong wrestling match with the notion of faith. My father worked so hard to make the world a better place. But was the world coming to its senses? Was it in fact becoming a better place? He wasn't sure, and we can hear him wrestling, as a composer, with the notions of faith, hope, and despair in piece after piece.

Maybe the principal source of tension in Bernstein's life — and therefore a main source of energy — was his relationship with his creator: both the spiritual and the biological one. Leonard Bernstein was raised by his Russian immigrant parents in a fairly traditional Eastern European Jewish environment — albeit in the Boston area. He went regularly to synagogue, had his bar-mitzvah, and grew up in the atmosphere of his father Sam's intense devotion to the Talmud. Sam Bernstein ran a successful hair and beauty supply business in Boston, and was proud to be able to pass such an excellent business opportunity along to his son.

But Leonard Bernstein didn't want to run the Samuel Bernstein Hair Company! He wanted to be a musician. For Sam, who grew up in the shtetls of Poland and Russia, being a musician meant being a nearly homeless person, who bummed from village to village, from wedding to bar-mitzvah, barely keeping food in his belly and shoes on his feet. The story goes that Sam refused to pay for his son's piano lessons. After Bernstein's famous last-minute debut in Carnegie Hall on November 14, 1943, some reporters challenged Sam about his reluctance to encourage his son's musical career, to which Sam famously replied, "Well, how was I supposed to know he'd turn out to be Leonard Bernstein?"

From the earliest conflicts with his father, Bernstein was already establishing a template for a lifetime of wrestling with his creator, of confronting authority. Over and over again, Bernstein turned to his father's beloved Hebrew biblical texts for inspiration and disputation. They appear in so many pieces over Bernstein's lifetime that taken together with the music, they form a kind of ongoing dialogue with God.

Bernstein dedicated his First Symphony, Jeremiah (1944), to his father. His use of the text from "Lamentations" served as a way to re-embrace his father, as much as to give his father a way to re-embrace his son. By the time he wrote Kaddish, however, Bernstein's mood was less conciliatory.

In this Third Symphony (1963), Bernstein's lifelong crisis of faith expresses itself through a titanic struggle over tonality. For Bernstein, the issue of tonality had taken on uncomfortably authoritarian overtones. A composer who wished to be taken seriously by the academic musical community in the mid-20th century absolutely had to forfeit tonality in favor of the 12-tone vocabulary. There was no middle ground. My father longed to be accepted in the halls of academia, yet he could not quite bring himself to stop writing a tune.

To my ears, Kaddish is an audible battle between tunes and 12-tones. Bernstein may not have resolved the problem for himself until his next piece, Chichester Psalms, completed two years later in 1965. He wrote that piece during a year on sabbatical from his musical directorship of the New York Philharmonic. Here is part of a poem he wrote for the New York Times describing what he did on his "vacation":

For hours on end I brooded and mused
On materiae musicae, used and abused;
On aspects of unconventionality,
Over the death in our time of tonality ...
Pieces for nattering, clucking sopranos
With squadrons of vibraphones, fleets of pianos
Played with the forearms, the fists and the palms —
And then I came up with the Chichester Psalms ...
My youngest child, old-fashioned and sweet.
And he stands on his own two tonal feet.

In a sense, Kaddish and Chichester Psalms can be considered one continuous work, for the latter piece is really a joyous, relieved resolution of the conflicts articulated with such anguish in the former.

If Bernstein's works dwelt exclusively on these notions of faith, hope, despair, and tonality, his music would be an unrelievedly earnest business indeed. But two ever-revivifying elements leavened his work: humor and rhythm. His irrepressible sense of the absurd drew him to musical theater, with its pedigree of Jewish immigrant irony, while his galvanic response to rhythm is what drew him to blues and jazz. Humor and rhythm lured him back to Broadway musicals again and again — in spite of being advised against it by his classically trained mentors. (Bucking authority again!) The next two works in The Philadelphia Orchestra's Bernstein Festival demonstrate some of Bernstein's most spirited work for the Broadway stage — not surprisingly in both cases, music for dance. It was the dance music he wrote for Jerome Robbins to choreograph that allowed Bernstein to write most ecstatically for rhythm.

On the Town (1944) was the first of three Bernstein musicals to be set in his adopted hometown of New York City. New York was the only city — possibly the only entity — with enough energy to keep up with Lenny. He loved New York City's snap and sizzle, its raucous honking middays, its lonely, moody midnights, and everything in between. We can hear all New York City's different moods right there in the notes of Bernstein's Three Dance Episodes from On the Town.

On the Town's score is groundbreaking in Bernstein's use of a symphonic composing approach. In the dance episode "Times Square," for example, we can clearly detect the many ingenious permutations of the four notes from the tune "New York, New York," which drive the music in the same way that Beethoven's four opening notes drive his Fifth Symphony.

By the time Bernstein wrote the score to West Side Story (1957), he had refined the technique even further. One of the many reasons I love my father's score for West Side Story is that we can so thoroughly enjoy it on different levels. We can let the music wash over us like a glorious tide, simply reveling in the rich melodies and propulsive rhythms. Or we can inspect more closely, and be amazed at the intricacy of its composition — at the grand, arching design behind it.

Three notes — just three little notes — provide the musical key to the entire West Side Story score. They're the opening notes of the show: a G, a C, and an F-sharp. We hear those three notes again and again, in endless anagrams and permutations, creating a kind of musical portrait ofambiguity.

This last interval of the opening motive, C to F-sharp, is a uniquely distorted one, neither major nor minor, known as a tritone. With the use of the tritone in West Side Story, Bernstein was turning to one of his favorite ways to express conflict: pitting tonality against atonality. The three-note motive simultaneously represents the harmony of the lovers and the discord of the street gangs. The lovers lean toward the harmonic stability of a major chord, while the street gangs tug the music toward chaos or dissonance. Bernstein's three notes, this tritone motive, act as the fulcrum on which these intensely opposing forces are beautifully balanced.

At the end of Symphonic Dances from West Side Story, Tony has been shot dead and Maria has vented her rage at both gangs: the equivalent of Mercutio's "a pox on both your houses" in Romeo and Juliet. As they all exit with Tony's body, we hear the final notes of "Somewhere," but this time that hopeful C-major chord is darkened by an F-sharp lurking in the bass fiddles and timpani. The tritone has returned. And that's the final message Leonard Bernstein leaves us with in West Side Story: a major chord full of longing for a better world, but with a dark warning that maybe what we wish for so desperately is out of our reach.

After the Kennedy assassination, my father's musical works grew darker, his assessment of our state of things grimmer. But he never stopped working toward the goals of brotherhood and world peace that he held so close to his heart. And in spite of his frequent gloom about the way things were going, he never gave up hope for a better world. After all, artistic creation is in itself a most profound act of optimism. But it was the act of teaching, and communicating with young people, that ultimately lifted Leonard Bernstein's spirits more than anything else in his life.

The educational component of The Philadelphia Orchestra's Bernstein Festival is "The Bernstein Beat." Bernstein's contemporaries and their children (my contemporaries) comprise a large group of enthusiastic fans, but now there's a new generation — and more generations to come — that are not so familiar with Leonard Bernstein. My friend Michael Barrett (who was my father's assistant conductor for many years) and I decided to do something about it. We devised "The Bernstein Beat," a concert for young people, consciously modeled after Bernstein's own Young People's Concerts, in which we introduce Bernstein's music to young audiences, and use it to explore the subject of rhythm. (As the narrator, I travel the world presenting the concert with different orchestras. Now it's Philadelphia's turn.)

The subject of rhythm automatically steered Michael Barrett and me toward Bernstein's liveliest works: music that inevitably gets kids (and grownups) bouncing in their chairs — a reaction we encourage. The concert features audience participation — including permission for the audience to shout "MAMBO!" at the top of its lungs right there in the concert hall!

It says much about Leonard Bernstein that his music can cover so much ground: that it can express the deepest questionings of the human soul and employ the most sophisticated symphonic techniques; that it can set every toe in the theater to tapping, and can also make children shout with joy. As his daughter, I can assert that that pretty well sums up the man himself.