The classical music industry places great faith in the Significant Birthday. Most mortals are permitted to tiptoe from one decade to the next with little or no fuss, but conductor Leonard Slatkin -- who turns 60 on Wednesday -- is gearing up for a huge celebration in his name, sponsored by the Kennedy Center and the ensemble he has served as music director since 1996, the National Symphony Orchestra.

On Sept. 26, the NSO will mark the official opening of its 2004-05 season with a concert and ball in Slatkin's honor at the Kennedy Center. There will be a lot of fancy guests -- violinists Midori, Joshua Bell, Itzhak Perlman and Pinchas Zukerman, pianists Jean-Yves Thibaudet, Joseph Kalichstein and Emanuel Ax, duo-pianists Katia and Marielle Labeque, flutist James Galway, conductor Murry Sidlin, and composer and performer Peter Schickele.

"I've been really touched by the people who want to come but simply can't, because of scheduling problems," Slatkin said in a recent telephone interview from London. "But I'm very happy with the guests we have. It will be the principal fundraising event of the season -- a little like eight years of the Kennedy Center Honors in a single evening!"

It is far from easy to assemble such a stellar cast (negotiating the egos of the guest violinists alone would tax the abilities of a skilled diplomat), and the fact that the concert is coming together at all is a sign of the affection and esteem in which Slatkin is held by his musical peers.

Slatkin, of course, will be working throughout his own party, serving as the evening's principal conductor. One can't imagine that he'd have it any other way; he has struggled long and hard and against what once seemed insurmountable odds to achieve his current eminence -- the music director of the most important orchestra in the capital city of the United States. And, as he mounts the podium to lead one of the grandest concerts of his career, he will have much to be proud of.

Perhaps his most significant accomplishment in Washington has been the radical improvement in the day-to-day playing of the NSO. When Slatkin was appointed music director-designate in 1994, this seemed an orchestra in trouble -- a collection of mostly fine artists who rarely managed to play a completely satisfying concert. Slatkin's predecessor, Mstislav Rostropovich, who led the orchestra from 1977 to 1994, was a spectacularly gifted cellist -- indeed, one of the great musicians of the century -- yet his conducting technique was sketchy and he seemed absolutely at sea in much of the standard repertory. Rostropovich's best performances, almost inevitably of Russian music, were charged with urgency and excitement, revelatory almost in spite of themselves. But his off nights -- and there were a lot of them -- were pretty dismal.

The NSO's playing picked up almost immediately when, after two seasons under visiting conductors, Slatkin took the helm in 1996. His sure ear, his clear beat and his brisk, authoritative comments came as bracing and salutary shocks for the orchestra. The reconstruction of the Kennedy Center Concert Hall the following year, while far from a complete success, permitted the musicians to really hear one another onstage for the first time, and the ensemble grew ever more flexible and cohesive. Several key appointments within the orchestra gave it a lusher, more diverse and sumptuous tone: By now, Slatkin has named the principal players for all five string sections (first and second violins, viola, cello and bass), three assistant principal string players, and principal bassoon, horn, tuba and timpani. There are 100 full-time players in the NSO; Slatkin has appointed 33 of them to their current positions.

And so, even when Slatkin isn't in town, this remains "his" NSO. "One of the things that makes me happiest about the orchestra is the way it sounds for everybody these days," he said. "Week after week, no matter who happens to be on the podium, it is a truly excellent ensemble -- and getting better."

A Noteworthy Start

This is not the first time Leonard Slatkin has built up an orchestra. His long tenure at the St. Louis Symphony was widely considered a triumph, for both the orchestra and Slatkin himself. He had originally come to the Midwest in 1968, 23 years old and fresh out of Juilliard, as an assistant to the late Walter Susskind, an old-world maestro who recognized Slatkin's talent and ambition. Beginning by conducting a Sunday afternoon concert series, Slatkin progressed to associate, associate principal and principal guest conductor before taking over as music director in 1979. He remained in St. Louis until 1996, directly before taking the Washington job.

During that time, Slatkin quite literally grew up with the orchestra, turning the St. Louis Symphony into a group quite on a par with the leading ensembles from New York, Boston, Philadelphia, Cleveland and Chicago -- the so-called Big Five. Indeed, Slatkin was the first native-born American to conduct all of these orchestras within a single year. Today, with Americans Michael Tilson Thomas leading the San Francisco Symphony, Robert Spano in Atlanta, David Robertson freshly ensconced in St. Louis and James Levine about to take the helm of the Boston Symphony Orchestra, such an accomplishment may not seem as impressive as it did once.

But -- with the towering exception of the late Leonard Bernstein, who really was a law unto himself -- our young "homegrown" conductors were once pretty much excluded by our own orchestras. Slatkin helped change all that, and a younger generation of musicians is in his debt.

Despite his burgeoning career as a guest conductor, Slatkin brought a refreshing commitment to the St. Louis Symphony. In an era when successful conductors tend to be jet-setting cosmopolites, flying here and there while maintaining their permanent addresses in a musical capital like New York or London, Slatkin settled in St. Louis and lived there until he came to Washington. He attended as many Cardinals home games as he could (he is still an avid sports fan); he knew where to find the best Italian food downtown and the best frozen custard on the South Side; he was very much a presence. It was once suggested that he had shaken hands with every man, woman and child in the St. Louis metropolitan area. Slatkin demurred: He was sure that there were some he had missed.

Through a combination of curiosity, directness, accessibility and charm, Slatkin managed to combine two distinct -- and usually incompatible -- objectives: winning over critics and music professionals with sophisticated, venturesome programming while building a strong following among local donors and subscribers, whose tastes tend to be deeply conservative. Some conductors object to the sort of politicking that is such an important part of running an American orchestra in the 21st century: Daniel Barenboim cited such "fritter" as one of the reasons he was leaving the Chicago Symphony. Not Slatkin. "Meetings, community work, local events -- they're all part of the job," he said.

To the Music Born

It has been well and truly stated that music is a glorious art and a difficult profession: Leonard Edward Slatkin was born into both of them in Los Angeles on Sept. 1, 1944. His parents were powers in the film music industry: His father, Felix Slatkin, was concertmaster at 20th Century Fox, while his mother, Eleanor Aller, was the first cellist at Warner Bros. In addition to his duties as a violinist, Felix Slatkin was conducting both the Hollywood Bowl Symphony Orchestra and the Concert Arts Chamber Orchestra; both parents were also founding members of the Hollywood String Quartet, an ensemble that became legendary for the passion and precision of its playing.

Visitors to the Slatkin house, in the mid-Wilshire district of Los Angeles, included artists as diverse as Igor Stravinsky, Arnold Schoenberg, Bernard Herrmann and Frank Sinatra. (No wonder Slatkin's latter-day tastes would be so wide-ranging!) He began playing the violin when he was 3, started piano studies at 12, took up viola at 14 and later studied composition with Mario Castelnuovo-Tedesco.

It was a remarkable upbringing by any standard but not an especially warm one. "The family always maintained a kind of professional relationship," Slatkin once said. "Because we all did the same thing, we were very sensitive to each other's criticism and kept things pretty much on a musician-to-musician basis."

Slatkin's brother, a cellist who calls himself Frederick Zlotkin, recalled a party for his father in which every member of the household wrote a variation on "Happy Birthday." "We were all so determined to outdo one another that we all wrote variations so difficult nobody could play them."

By all accounts, Leonard Slatkin was a solitary young man. "I liked isolation then, and I still do today," he told me the first time I met him, more than 20 years ago. "There is a difference between being alone and being lonely. It's true that I had few close friends. But I had my scores and recordings, which allowed great composers to speak with me. To this date, I feel in close communication with my composers; when I am preparing a piece, something, somehow, tells me when I am on the right track."

He seems much less the loner these days, a proud father and husband dividing his time between the Maryland suburbs and a vacation home in Florida. At one time a somewhat disheveled and vaguely paunchy figure, he has matured into a trim elegance. As a fierce champion of music education, he has worked to rescue funding for the D.C. Youth Orchestra, made guest appearances with groups ranging from the U.S. Naval Academy Band to the Fairhill Elementary School Chorus and Band in Virginia, and conducted benefit concerts for various orchestras, both amateur and professional, throughout the area. To help prepare young people who are learning to lead orchestras, he has founded the National Conducting Institute with the American Symphony Orchestra League.

Moreover, he is probably the best public "explainer" of music since Leonard Bernstein, able to prepare a dubious audience for even the most recondite new composition; he speaks in full paragraphs, with wit and incision. In short, Slatkin is what the trade calls a "good citizen" -- and in a time when classical music is struggling on almost every level, his steady, friendly advocacy takes on renewed importance.

He has some shortcomings, of course. He likes to work with soloists he knows and, at times, he has seemed overzealous in his promotion of artists with distinctly minor gifts. The pianist Jeffrey Siegel, for example, impresses some listeners as quite literally heavy-handed. No matter -- Siegel was the best man at two of Slatkin's three weddings, and he will be playing in the gala. The current Mrs. Slatkin -- soprano Linda Hohenfeld -- has appeared with the NSO on several occasions, with mixed results. Slatkin's more grudging critics have viewed these artistic decisions as his attempts to establish himself as a musical power broker, in the tradition of the late Isaac Stern (who exercised considerable -- some would say scandalous -- influence on who did and didn't get to play on the stage of Carnegie Hall). Myself, I've always seen such generosities as genuine, heartfelt expressions of loyalty to the people who have believed in him over the years -- a trait more admirable in a human being than in a music director, perhaps, but far from a capital crime.

Slatkin's taste in contemporary music is unreliable: He generally shies away from distinctly original new work and leans toward a sort of eclectic pastiche. Moreover, some of the American composers of the recent past he has championed -- Samuel Barber, William Schuman, the symphonic Bernstein -- are beginning to seem as overrated today as they may have been underrated when Slatkin started putting them on his programs.

Then there are times when one senses that Slatkin is more interested in making "news" -- The Beethoven "Tenth"! A Percussion Festival! -- than he is in exploring the deepest recesses of the repertory's masterpieces. When listening to Gustav Mahler's much-touted (by Slatkin) arrangements of Beethoven's symphonies last season, one felt that the younger composer's amendments both bloated and depleted the originals. At best, they were novelties; at worst, desecrations. (Dvorak's cantata "The American Flag" impressed me as perhaps the worst piece ever written by a major composer at the peak of his powers: some neglected music deserves it.) Slatkin sometimes seems more interested in new, catchy ideas than in their innate quality, satisfied with merely being "bright" or "clever" when he has the capacity to be great.

And yet the fact remains that Slatkin occasionally comes up with some real "finds" -- Mexican composer Silvestre Revueltas's shatteringly powerful "Noche de Los Mayas," which all but blew the Kennedy Center roof off in 2001; Gabriel Pierne's tender, intricate and beautifully proportioned 1997 cantata "The Children's Crusade"; and admirable works by American composers Arthur Foote and Walter Piston, both of which the NSO took on a European tour. Better, finally, that Slatkin errs on the side of experiment, rather than simply following in the paths of maestros past.

Following His Lead

The next years ought to be important ones for Slatkin and his orchestra -- and who can predict where they will go together? Many of Slatkin's tastes have changed over the past decade. In 1996 he gave an interview in which he called Mahler "overrated." Five years later, he was leading idiomatic and meltingly beautiful renditions of the middle symphonies. He once declared Philip Glass a "fraud"; next year, he will conduct a newly commissioned work from the composer, a symphony of which he speaks with genuine excitement.

In the meantime, he has remained steadfast in his championship of the composers he considers neglected -- Rachmaninoff, Vaughan Williams, Elgar and the earlier Americans -- as well as many others who need no special pleading. He brings excitement and a dash of good old Hollywood razzle-dazzle to the film scores he conducts. He is an expert accompanist who knows innately when to lead and when to defer to his soloists. He brings humor and heartiness to the classical repertory, especially in Haydn, Mendelssohn and early Beethoven. When Slatkin came to Washington, he said his job with the NSO was to "instill more of a sense of unity and consistency from one period of music to another, one piece to the next." In this, he has succeeded brilliantly, combining technical skill with American pragmatism.

"Professional musicians want to see the goods, through your hands and gestures," he once said, in a statement that might serve as his credo. "They don't want lectures. They need to hear from you what is wrong -- and why. They're not so concerned with what is right -- although a compliment here and there never hurts. They want you to tell them about the balances, about whether a note is sharp or flat. If something isn't together, you have to tell them why that is and offer a solution."

Here's to many more such "solutions" from Leonard Slatkin.

Music director of the NSO since 1996, Slatkin's Sept. 1 birthday will get a belated, and star-laden, celebration on Sept. 26.Slatkin conducts his farewell concert with the St. Louis Symphony in 1996.During the National Conducting Institute in June, Slatkin shares ideas with Carolyn Chi-an Kuan, left, and Daniel Wachs, among others.