Sidney Bechet, the moon-faced soprano saxophonist from New Orleans, who was among the first to introduce American jazz to Europe, once explained why he had to play: "Me, I want to explain myself so bad. I want to have myself understood. And the music, it can do that. The music, it's my whole story."

Bechet's credo has been at the core of American popular music from its vigorously diversified beginnings. "Art music" or "serious music" was for the relatively few. It was predominantly shaped by European dictates and required specialized and expensive training.

But popular music, starting with folk songs, was unabashedly homemade and invited democratic, communal participation - whether in a barroom, a logging camp or an Appalachian hollow.

And for the singer or player of this pridefully indigenous music, it has always been a way of getting himself understood. Not only himself but also the ways of life, the priorities, the complaints of the particular segment of the American grain that nutured him.

In the isolated mountains and backwoods of the South, for example, transplanted and trasnsmuted Scotch-Irish-English ballads spoke from the beginning for the stubborn independence of the people there are buttressed their sense of identity, of specialness.

In the East, folk tunes - self-celebration - and topical songs, roisterously vocalized in taverns and hawked on the streets as cheap broadsides, flourished during the Colonial period.

Even Puritan ministers could not eliminate the desire of settlers in the new world to explain and celebrate themselves through music. One such minister spoke bitterly in 1720 of the sounds of the common man: "Left to the mercy of every unskilled Throat to chop and alter, twist and change, according to their odd Humours and Fancies, they sound like Five Hundred different tunes roared out at the same time."

Through the American centuries, similar jeremiads have been directed at various genres of popular music by clergymen, educators and others fervently convinced that music which is not "serious" or at last "respectable" can corrode the spirit and numb the mind.

So, in the early 1920s, jazz was accused of being a direct cause of crimes of passion.

And in the early 1970, Richard Nixon, among others, was so concerned that rock lyrics were inciting antisocial behavior - from draft resistance to marijuana consumption to profligate sex - that the Federal Communications Commission tried to censor rock recordings. Not for obscenities, which were, in any case, forbidden on the air, but for heresy.

The rock musicians, however, were actually doing - for a much larger, nationwide audience - what Appalachian songsters, New England seamen, western wranglers and other popular bards had been engaged in long before. They were explaining themselves through their music, and they were also forging links of communication with others who shared their priorities, hopes, fantasies, ways of wit and ways of coping with loss.

American popular music has not, of course, always been controversial. The music of Stephen Foster, for instance, was an extension of a significant mid-19th Century development, the advent of "genteel" songs. These, as American music scholar H. Wiley Hitchcock points out, "were aimed at the home - at the typical American parlor, with its little square piano or reed organ, its horsehair-stuffed sofa, its kerosene lanterns and candlelight." Music for devoted amateurs, its texts were "generally one step removed from ordinary American speech."

This "genteel" music also expressed the values - somewhat sentimental and idealized - of a particular group of Americans.

So did the American phenomenon of vaudeville that grew in the "concert saloons" of the 1850s, went on to flourish in theaters and expired when the movies permanently distracted its audiences.

Vaudeville and saloon songs were the popular music of the burgeoning city folk, who like their fun in overflowing portions and preferred expansively romantic ballads, along wtih rollicking novelties, bawdy and otherwise. For those in places far from "live" vaudeville, there were sheet music and, in time, recordings. A national popular music was being created.

With the advent of radio and the movies, the nationalization of the pop song was greatly intensified.

While parts of the population held on to and kept regenerating their own musical hearitages - white country and western music, black sounds and rural regional ballads - Tin Pan Alley, the Broadway stage, the Hollywood studios and the radio networks were fashioning what most Americans now define as popular music.

These mass-production sources also shaped and reflected certain popular values. Romance overshadowed all. Rather sanitized, dream-like romance, however, by contrast with the direct, nearly palpable expression of earthly love in black music.

Optimism was another basic ingredient. Even during the Depression, "Brother, Can You Spare a Dime?" was a rarity. In this music, America was still the land of infinite possibility where, over the rainbow, one might find a million-dollar baby in a five-and-ten cent store.

Departing from the sounds and rhythms of the Hollowood and Broadway stage, the songs of the 1960s, broadly called "rock," incompassed elements of blues, country and Hispanic music.

Rock was and is in defiant opposition to the polished, skillfully crafted music of Lorenz Hart, Oscar Hammerstein, Richard Rogers, Harold Arlen and others who had previously set the standards for American popular song.

Often raw and poundingly loud, rock rebelled againt both the music and the values of the older generations. In these songs, sex, while not pornographically depicted, was much more openly experienced and enjoyed. Optimism was also much tempered. Life was no longer an upwardly mobile crystal staircase in a land of unending plenty. Ecology came into popular music, as did a steady electronic indictment of unexamined materialism.

The music itself was ebullient and became a common language, a way of mutual identification, for hordes of the young denouncing the herd instinct of their elders.

The main directions of our music will change again - as always, unpredictably.' In the meantime, while mass popular music remains within the flexible confines of rock, a growing number of younger musicians are exploring older musical roots. A number of country players, such as Willie Nelson, are discarding string sections and complex recording techniques, opting instead for simpler songs and backgrounds with more traditional sounds.

Black musicians, such as trumpeter Leo Smith, while forging ahead with avant-garde jazz, are simultaneously studying the heritage available to them from the work of Louis Armstrong and other patriarchs of jazz. And Rany Newman, among other popular baladeers, is exploring a conversational, story-telling style that picks up the way a wide range of Americans actually talk and think.

Wherever American music goes, it will continue to be created in a multiplicity of idiomatic tongues, and the best of its makers will keep on exemplifying the dictum of jazzman Charlie Parker: "Music is your own experience, your thoughts, your wisdom. If you don't live it, it won't come out of your horn." Or your guitar. Or your voice.