The media in this country, I suspect, have led people to think of Bernstein only as a conductor. Cameras are fondest of people in action, and Bernstein on the podium was action personified. Eyes closed, jaws clenched, hair mussed, sweat pouring from his brow - it was an image no editor could resist, and it circulated so widely, over so many years, that it came to symbolize the art of conducting. In an earlier day, the icon would have been Toscanini or Stokowski; if a child today were asked to draw a picture of a ''maestro,'' the result would probably look more like Bernstein than anyone else.

Regarding Bernstein's conducting style, the image is not altogether inaccurate. He was, more than anything else, an emotive musician. For him, an orchestral score was not simply a combination of notes that needed only to be sounded in order to be realized. It needed also to be interpreted, marked boldly with the personality of its performer. Bernstein respected composers' instructions, but only to a point. In the long run, what the music ''expressed'' was what he chose to make it express, and more often than not this had a great deal to do with what he was actually feeling at the moment. Last week's television tributes offered plenty of examples: a mask of anguish during a dark episode in a Mahler symphony, a glow of serenity at a cadence in Mozart, a look of giddy excitement - physical, almost sexual - as a passage in Beethoven builds toward climax. Bernstein was not mugging for the camera when these shots were taken; he was making music, his way, and what some critics decried as theatrics were in fact an integral part of the process.

But as vivid as the trademark portraits are, they represent only a fraction of what Bernstein was all about. Putting pen to paper is not nearly so photogenic as standing before a 100-piece orchestra and single-handedly whipping a performance into shape. Even less appealing, from the camera's point of view, is the quiet concentration that makes writing possible. Bernstein engaged in this activity as well. You wouldn't know it just from looking at the pictures, but he took it far more seriously than he did his conducting.

Two years ago on this page, in commenting on the Bernstein phenomenon on the occasion of his 70th birthday, I offered a brief assessment of his compositions. He is likely to be remembered as ''a facile composer of only limited range and depth,'' I wrote.

I still think that, although it is certainly my hope that his ''deep'' concert works will someday get a share of the attention that his enormously popular theatrical pieces now enjoy. Bernstein, of course, is the creator of ''West Side Story'' and of ''Candide.'' It is perhaps difficult, when listening to an amateur chorus slug its way through ''Here Come the Jets,'' or when hearing the glittery theme from the old Dick Cavett television show, to think of Bernstein as a musical brooder.

But balancing his light works is a considerable body of material whose content is definitely weighty. In concert halls worldwide, Bernstein's rhapsodic and hauntingly lyric ''Chichester Psalms,'' from 1965, has received as much play as has his frothy 1944 ballet ''Fancy Free.'' His 1971 ''Mass'' - a theater piece, not a setting of the traditional Roman text - has been much performed at least in excerpt, and audiences in St. Louis have in recent seasons been exposed to the 1946 ''Facsimile'' ballet, the sober 1954 film score for ''On the Waterfront, '' the 1954 violin concerto titled ''Serenade'' and the 1981 ''Halil'' for flute and orchestra. Generally neglected, however, are the three symphonies into which, relatively early in his career, he invested so much energy and private emotion.

The first, subtitled ''Jeremiah,'' is a three-movement piece for mezzo-soprano and orchestra based on the lamentations of the biblical prophet; it was written for the most part during the summer of 1939, when Bernstein was unemployed, and it won the New York Music Critics Circle Award after its premiere in 1944. The second, based on W.H. Auden's poem ''The Age of Anxiety,'' dates from 1949, the year after he toured war-torn Europe and performed for, among other audiences, survivors of the concentration camps. The third, a stylistically eclectic work that involves soprano soloist, narrator and choruses, is the '' 'Kaddish' Symphony'' of 1963; upon its premiere in Tel Aviv it was regarded as almost blasphemous, not because of its many references to jazz rhythms but because of its overall philosophical tone.

''Although all of Bernstein's concert works deal with what he calls 'the problem of faith,' '' Joan Peyser wrote in her still-controversial 1987 biography of the composer, ''it was only after the early 1960s that he set himself up in a confrontational posture with God. And the first of the works in which he did this was 'Kaddish.' '' As music and as idea, ''Kaddish'' is profound, but only relatively more so than the ''Jeremiah'' and ''Age of Anxiety'' symphonies.

These works are long and complex, not the sort of thing for an audience that likes its music short and snappy. But they represent, more accurately than anything Bernstein produced for the theater, the real essence of his creative personality. They say something about what drove him, about what he pondered when he wasn't distracted by the glare of the limelight. Perhaps it is because they are, in so many ways, such ''difficult'' pieces that they remain more talked about than heard.

All of them have been recorded. Under Bernstein's baton, the St. Louis Symphony committed ''Jeremiah'' to disc as long ago as 1945, and Bernstein recorded it again with his own New York Philharmonic in 1961. With the New York Philharmonic, too, Bernstein recorded ''Kaddish'' (in 1964) and the ''Age of Anxiety'' (in both 1950 and 1965), and in 1977 he recorded all three symphonies with the Israel Philharmonic. But only the 1977 versions are currently in print. They are stellar performances, but seldom aired on the radio and hardly ever emulated in the concert hall.

Fortunately, Bernstein's books are more readily available than his most serious musical efforts. They are not so numerous as his compositions, but they, too, range in subject matter from breezy to knotty, and taken together they form a fair digest of Bernstein's thinking about the art he practiced.

Easiest to read - ideal for people just starting to immerse themselves in classical music - are the three he wrote when he was music director of the New York Philharmonic. The 1962 ''Young People's Concerts for Reading and Listening'' is a byproduct of the talks he gave in conjunction with both live and televised performances for children; ''The Joy of Music'' (1959) and ''The Infinite Variety of Music'' (1966) are chatty but insightful introductions intended for audiences whose enthusiasm is greater than their knowledge.

Harder to get through, but no less rewarding, is ''The Unanswered Question,'' a compilation of the Charles Eliot Norton lectures Bernstein gave at Harvard University in 1973. There is nothing highfalutin about Bernstein's attitude here, but he is, after all, addressing a group of bright young college students. The argument of his ''Unanswered Question'' can be traced in the chapter titles. He begins with the basic workings of music - ''Musical Phonology,'' ''Musical Syntax'' and ''Musical Semantics'' - then proceeds to a discussion, in a section called ''The Delights and Dangers of Ambiguity,'' of how technical devices are put to the service of art. He gets responsibly sociological in ''The 20th-Century Crisis.'' And finally, in ''The Poetry of Earth,'' he deals with what he regards as music's most fundamental values.

Bernstein's ''Unanswered Question'' is filled with references to scholars in the fields of linguistics and psychology. Its ideas are complex, and thus so is the language Bernstein uses to express them. But the thinking that guides these ideas is as clear as a bell, and even when it is complex the language is eloquent and heartfelt. In his lofty intellectual endeavors, too, Bernstein was ever passionate.

His only other book is one titled ''Findings,'' a 1982 collection of short pieces he'd written over the years but never before brought between hard covers. Some of the items are pure fluff, some of them are of purely personal nature, and many of those that deal with music are very narrow in scope. But among the odds and ends are at least a few gems that say as much as does the whole of ''The Unanswered Question.'' My favorite is a three-line scribble - a poem, I guess you could call it, or a credo - he set down in 1967: "Life without music is unthinkable, Music without life is academic. That is why my contact with music is a total embrace."

Seduced as they are by what the media give them to see, people tend to overlook the portion of Bernstein's work that demands time, effort and sympathy. Bernstein's image - intense, sweaty, sexy - will endure. So will his music-making; while performances are ephemeral, recordings of them are not, and as a recording artist Bernstein was almost as prolific as the late Herbert von Karajan.

What will endure the longest, though, will be not what is preserved on tape but what is preserved on paper.

At the time, Bernstein was 71 years old and apparently healthy. The worldwide hoopla that had marked his 70th birthday was fading into memory, and the next major round of festivity - a co-celebration in 1993 of Bernstein's 75th birthday and the golden anniversary of his legendary debut with the New York Philharmonic - was barely in the planning stages. Except for the music itself, Slatkin had no particular reason to contemplate and eventually build a program made up of works by Bernstein. But the music itself is reason enough.

Repeated often on television and on the jackets of his many recordings, Bernstein's image has been deeply etched in the memories even of those whose interest in music is only casual. It is a charismatic image, alternately soft and severe, often lubricated by perspiration, always illuminated from within. And it is an image that says a great deal about how Bernstein approached the act of music-making. For Bernstein, it had to be a total experience, one that involved not just his intellect but also his emotions and his whole physical being. The extent to which this had an effect on his interpretations is debatable; it seems beyond dispute that Bernstein's personality - so manifest in his performances - had a lot to do with his status as a 20th-century musical superstar.

The stardom, ironically, was granted only to Bernstein the conductor. Bernstein the composer was just as gifted, just as worthy of attention. But he functioned in a culture that perversely grants less favor to those who create music than to those who merely re-create the music of others.

''The only good composer is a dead composer'' is not a slogan you'll see hanging in the offices of orchestras, record companies and classical music radio stations these days. Its sentiment applies, though, to judge from institutional programming in general over the last two decades, and it is espoused almost as much in Europe as it is in this country. Bernstein's baton was in great demand right until the end; usually it was hired - for a handsome fee - to govern the pace not of Bernstein's own work but of some blue-chip masterpiece by Beethoven or Mahler. Now that Bernstein, too, is dead, will he finally be recognized as an important composer?

My guess is that, yes, he will. And my focused guess is that he will be recognized, in the long run, for pieces other than those that today are his best-known.

That Bernstein's most famous music had long been the score he wrote for the Broadway theater was ''a fact that (caused him anguish,'' Joan Peyser wrote in her 1987 biography. Leonard Slatkin, who made Bernstein's acquaintance just five years ago, supports the claim. ''I don't think he regretted having written 'West Side Story,' '' Slatkin said last week, ''but he told me he would gladly trade all the 'West Side Story' performances in the world for just a few readings of his 'Jeremiah' symphony. There's no question about it; his theatrical music did displace his more serious works on American orchestral programs.''

One of the reasons for that, Slatkin suggested, is the evergreen popularity of the ''Symphonic Dances from 'West Side Story' '' and - in the same vein - the energetic ballet ''Fancy Free,'' the frothy overture to the opera ''Candide'' and the tuneful ''Dance Episodes'' from the Broadway show ''On the Town.'' Assuming the performance is at least adequate, this music is almost guaranteed to be a hit with any audience and doubtless that adds up to something in an orchestra's ledger book.

Indeed, it is precisely repertoire of this sort (the three last-mentioned works, plus the 1946 ballet ''Facsimile'') that constitutes the only all-Bernstein album Slatkin and the St. Louis Symphony have recorded. But another reason for the general neglect of Bernstein's serious compositions, Slatkin said, has been - until last year - Bernstein's own magnificent presence on the podium.

''There are just not that many composers around today who are really good conductors,'' Slatkin said. ''And the few that exist are, in a way, intimidating. Aaron Copland was a conductor, but no one ever thought of him as being especially competent, and so the rest of us felt free to take on his music. But with Bernstein it was different. So long as he was on the scene, how could we dare perform - let alone record - these pieces?''

Slatkin has been grappling with that question for some time now, and it is to his credit that - even before Bernstein's death - he found an answer.

Bernstein's 1963 ''Symphony No. 3 ('Kaddish')'' is a work that Slatkin prefers to leave to others, mostly because of its funereal text. Slatkin's father, once the concertmaster of the St. Louis Symphony, passed away in the same year that Bernstein composed his elegy for John F. Kennedy. Almost three decades later, the words of the Kaddish prayer - the same words he recited over his father's dead body - for Slatkin still strike uncomfortably close to home. But Slatkin has felt that Bernstein's other two symphonies - the 1942 ''Jeremiah,'' a work for orchestra and mezzo-soprano based on the lamentations of the biblical prophet, and the 1949 ''Age of Anxiety,'' a purely instrumental work inspired by the W.H. Auden poem - were well within his emotional reach. Over the last three or four seasons he had been conducting the music in Europe. So why not, he mused, do it in St. Louis? Since Bernstein as a guest conductor was clearly unaffordable by the St. Louis Symphony, how else - unless Slatkin did it himself - would this ''important'' music be heard in Powell Hall?

Along with the angular and brooding ''Age of Anxiety,'' the upcoming program includes the 1949 ''Prelude, Fugue and Riffs'' and the 1977 ''Songfest.'' The former - written for jazz clarinetist Woody Herman, revised for but later dropped from the Broadway musical ''Wonderful Town'' - certainly counts among Bernstein's lighter pieces. The latter is a probing cycle of songs whose eclectic materials (the poets range from Walt Whitman and Langston Hughes to Anne Bradstreet and Gertrude Stein) represent what Bernstein saw as the essence of modern American culture; it has optimistic moments, but on the whole it is far less cheery than contemplative.

The three pieces together add up to a fair portrait of a musician whose personality was, to say the least, complex. Bernstein invested most heavily in works he said were ''about the crisis of faith,'' yet he could not refrain from writing music in which soul-searching figured not at all. Indeed, one suspects he needed to produce lightweight music in order to relieve internal pressures brought on by his serious efforts. It seems not just coincidence that the second symphony and ''Prelude, Fugue and Riffs'' date from the same year, that while Bernstein was laboring over ''Songfest'' he was also penning a musical comedy titled ''1600 Pennsylvania Avenue.''

Orchestras around the country will doubtless continue to perform the Bernstein favorites, and there is no reason why they shouldn't. But the future, I think, will see increased attention paid to Bernstein's darker side, and audiences will eventually realize that there was much more to this man than hummable tunes and perky rhythms.