The Boston Pops, which celebrates its 100th anniversary today with a concert at the Lincoln Memorial, is more than an orchestra. It is a revolutionary concept in the marketing of music. Appropriately for a concert at the Lincoln Memorial, it will celebrate an idea that made music free.

Today's concert is the kind that made the Pops a major influence on the mass audience -- outdoors and gratis. It will be carried nationwide by PBS at 8 p.m., and this easy use of the electronic media is another hallmark of the Pops' longstanding, special access to the heart of America. When I was a boy in Boston, those free outdoor concerts were the only live classical music I could afford, and there were thousands like me.

We would arrive hours early at the Esplanade, a long, grassy park that runs alongside the Charles River and is now reached from the Back Bay by a footbridge appropriately named for Arthur Fiedler. Some would even stake out their territory and then wander off to one of the spots where swimming in the river was allowed in those unpolluted days.

There would be blankets, picnic baskets and music lovers of all classes politely maneuvering for the best positions on the almost endless lawn. And finally, when Fiedler mounted to the podium in the Hatch Memorial Shell and raised his baton, it was amazing how quiet those thousands could be. Memories of those summer nights are now a medley of sensory impressions: grass, fresh and clean-smelling; clusters of friends; bright starlight overhead; the "William Tell" Overture or "The Stars and Stripes Forever" drifting in from the distance. Music will never sound quite as it did then, and no one will ever look as much like the archetypal conductor as Arthur Fiedler.

At home, before and after the short season of outdoor music, Fiedler was a presence on the radio and the windup Victrola, with "Rhapsody in Blue," the first jazz music to be recorded by a symphony orchestra, and "Jalousie," the first orchestral recording to sell more than a million copies. He introduced the world to Leroy Anderson, a clever young man whose "Jazz Pizzicato," "Sleigh Ride" and "Waltzing Cat" had the pop charms of novelty, brevity and catchy rhythms with the classical attractions of formal discipline and brilliant orchestration. Most memorable, perhaps, was "The Typewriter," which included a no-kidding typewriter in the percussion section. After Fiedler discovered Anderson in 1936, there was rarely a Pops program without some of his music.

But those long-ago concerts were not all fluff; Liszt, Brahms, Beethoven and Rossini made regular appearances. Bach's "Air on the G String" was a hardy perennial, and so was his "Little Fugue" in G minor, written for organ but well adapted for orchestra. A classical concerto would usually occupy the middle section of an evening at Pops, most often featuring a relatively unknown young soloist who might go on to stardom.

The little goodies -- Leroy Anderson's novelties and arrangements of pop tunes -- usually came at the end, and while we were patiently waiting for dessert we were given some very substantial music. Many of us developed a taste for the serious stuff; Fiedler's orientation was partly that of a missionary, and he made countless converts. He gave John Williams a hard act to follow, and he set a pattern and a standard imitated (in their lighter moments) by orchestras all over America.

The idea of the Boston Pops, in 1885, was as revolutionary as the Boston Tea Party a century earlier. The cream of Boston society attended the Pops' opening night on July 11, 1885, and photos from the early years show a substantial part of the audience in tuxedos. But from the beginning, a basic idea of these concerts was to develop a new, non-elite audience. Ticket prices for the original concert ranged from 25 to 50 cents. The bottom price held firm into the 1930s, though the top price doubled for the best seats -- at tables on the main floor, where the real profits were made on the sales of refreshments.

For the first 45 years, the Pops was exclusively an indoor phenomenon; then, in 1930, Fiedler brought it outdoors. He had been a Boston Symphony violinist who aspired to be a conductor, and the Pops' Esplanade tradition might be labeled "Fiedler's Revenge." He had been turned down as conductor of the Pops a few years earlier, had organized his own orchestra and begun to give free concerts on the Esplanade. These were such a success that Fiedler was appointed as the Pops' conductor -- a post he held for the next half-century -- and the outdoor music was a part of the package. The bottom ticket price fell from 25 cents to zero, but the audience grew enormously, and many of its members developed a music hunger that later brought the Boston Symphony rich dividends.

The Boston Pops orchestra that everyone knows and loves is one of the world's greatest -- the Boston Symphony, minus a few of its principal players who perform chamber music rather than waltzes, marches and Beatles numbers, in its off-season.

But there are really two Pops orchestras. When the Boston Symphony is busy at Tanglewood, a corps of free-lance players (called the Pops Esplanade Orchestra) fills in. For today's concert, members of the BSO will be playing. There will be a sing-along (including "We Are the World"), with a 350-voice choir recruited in Washington to lead the spectators. The concert will end (as such concerts almost have to) with "The Stars and Stripes Forever," and along with some Disney songs and music from "West Side Story" (which hasn't been played outdoors here since July 4), the program will include a lot of music by the orchestra's current conductor -- nothing from "Star Wars," but music from "E.T.," his "Cowboy" Overture, his Olympic Fanfare and Theme and "America: The Dream Goes On," sung by (who else?) John Denver. The program will be all American -- a contrast with the Pops first program a century ago, which included not a note of American music.

It will be slick, professional, calculated to please a live audience of 200,000 and a television audience of millions -- a textbook example of mass marketing.

The Pops marketing concept is, ultimately, one of the factors that helped to make the Boston Symphony a great orchestra with one of the world's most loyal audiences. The basic idea was stated, with disarming simplicity, by Henry Lee Higginson, the founder of the BSO, when he announced his plan for a new orchestra in 1881.

His plan, he said, was "to give in Boston as many serious concerts of classical music as were wanted, and also to give at other times, especially in the summer, concerts of a lighter kind of music, in which should be included good dance music." The reasons for this innovation have some validity wherever classical music is played, but nowhere more intensely than in this country. Hidden in the subtext of Higginson's plan were a number of other propositions:

*That the traditional class structures of music were (and had to be) breaking down; if symphony orchestras were to survive in a democracy without royal subsidies, they must attract a mass audience.

*That musicians needed to earn money in the summer as well as in the traditional winter season.

*That any music worth performing at all deserved a first-class performance.

Most important was the promotion of symphonic music for the masses. The economics of classical music had suffered rude shocks in the century before the founding of the Boston Pops. Permanent musical establishments existed almost exclusively at the courts of Europe. Sometimes the king or archduke was a music lover; sometimes he was merely showing off. But Louis XIV had had his own orchestra, and he was the model for all enlightened monarchs who came after him.

When revolutions began to unseat the monarchs, the new democratic governments of Europe took over the royal job of supporting symphony orchestras and opera companies. But in the United States, no such tradition existed. Government subsidy for the arts -- taken for granted in Europe -- is still a controversial subject in this country, more than two centuries after the American Revolution.

To some extent, industrial magnates and corporations -- the royal families of America -- have picked up the slack, but U.S. orchestras have depended on ticket sales to a degree unthinkable in Europe. This means that European orchestras can be more adventurous in their programming and American orchestras have to build new audiences, with pops programs as a key part of their strategy.

But there is more to it than mere economics; the Pops philosophy involves a sincere and spontaneous affection for all kinds of music, not merely that which is monumental, calculated to elevate the spirit to higher things, prestigious for its sponsors and patrons, or imbued with the special charisma that great age can give to almost anything. And not merely that which is trendy this month, familiar on top-40 stations, enhanced by a "hook" that keeps it running through your brain or dressed up in a "new sound" that will be terribly old-fashioned next year.

Fiedler loved -- and his orchestra played -- music of all kinds, from a Bach fugue to a tango. "All music is good," he once said, "except the boring kind." It may sound like a sweeping statement, but he spent a half-century demonstrating its truth.