Almost from its beginning, the 20th century became the Age of the Americas in popular music. It took more time, two world wars and the Russian Revolution to make the Western Hemisphere a major power in classical music, but by now we can say that it has happened.

The tango hit Europe only a bit after ragtime, and each became an instant craze. While their fellow-citizens were puzzling over the new dance steps, such composers as Stravinsky and Debussy began to use the exotic musical forms in classical compositions.

Since then, groups from Sweden to Japan, and even some dissidents in the Soviet Union, have been working hard to sound like North or South Americans playing jazz, rock, samba and cha-cha. Italian sopranos forgot about being Mimi, tackled the role of Liza Doolittle and tried to cope with the tongue-twisting lines of "In Spagna s'e bagnata la campagna (The rain in Spain stays mainly in the plain)." Jacques Brel himself took the title role in the original Paris cast of "L'Homme de La Mancha."

At the same time, Americans have worked hard to sound like Austrians, Poles or Frenchmen playing Haydn, Chopin and Berlioz. Traditionally, Europeans have felt that classical music was uniquely theirs, and Americans, North and South, have tended to agree. It was true (or more true than otherwise) in the long period from Palestrina to Brahms while this hemisphere was being discovered and winning its independence from the Old World. It is true no longer, and we have potent reminders all around us right now in the form of two festivals: the 13th Inter-American Music Festival, which is happening through May 16, mostly at the Kennedy Center and the Organization of American States, and the 39th annual Festival of American Music, which will be continuing on Sunday nights through May 30 at the National Gallery. Another mark of American music's coming of age will be performed by the National Symphony Orchestra next week: the Piano Concerto in G in which Maurice Ravel shamelessly imitated George Gershwin.

As far as we know (it usually takes a while for the world to notice), the Western Hemisphere has not yet produced a musical genius comparable to Bach, Mozart and Beethoven. But on the more modest level of Mendelssohn, say, or Poulenc, where most of the permanently valuable repertoire has been produced, the world's musical center of gravity seems to have shifted to North and South America.

This has happened in spite of the fact that European countries (particularly those with ministries of culture and government-operated radio networks) tend to do a lot of public-relations work for their native composers, while American audiences still tend to feel slightly uneasy about the music of their fellow-citizens, unless they happen to be named Copland or Bernstein.

Music is an international language, though each nation tends to speak the language with its own accent: Italy with lyric grace even in atonal idioms; Germany and Austria with solid, intricate structures; France with lightness of sound and witty, clever style; Russia with emotional intensity and muscular orchestration.

America is an heir to these traditions and has spoken with all these accents while adding its own--largely derived from the strong African roots of our folk and pop music. At its best and most individual moments, American music offers high energy, subtleties of rhythm not native to Europe and a special expertise with percussion instruments, not to mention a wealth of folk melodies and techniques borrowed from jazz.

The accents of North and South America differ, but they are often closer to one another than either is to Europe. The classic example is probably Aaron Copland, who learned much about the classical use of folk material from Carlos Chavez of Mexico, and paid him a sort of tribute in his early experiment with folk idioms, "El Salon Mexico."

Some Europeans notice and appreciate the unique qualities of American music. American artists who tour overseas report a steady demand for American music from audiences there--something they seldom hear at home. Washington pianist Alan Mandel has organized American music festivals in Scandinavia and Egypt in the past few months. "It's easier over there than it is here," he reports.

But Europe has also transplanted its own musical culture to the New World. Eminent European composers began moving to the United States for prolonged stays around the turn of the century, beginning with Dvorak and Mahler, who served as conductors of the New York Philharmonic, as Pierre Boulez did in the 1970s. Others, such as Luciano Berio and Gian Carlo Menotti, have been so active in the United States that they practically enjoy dual citizenship.

In a sense, American classical music came of age because Hitler and Stalin drove talented people into exile. Thus, in the early 1940s, Arnold Schoenberg, Igor Stravinsky and Sergei Rachmaninoff, the symbolic figureheads of three completely different schools of composition, were living a few miles from one another in Los Angeles. At the same time, Darius Milhaud, another symbolic figure, was up north in Oakland, teaching at Mills College, and Be'la Barto'k and Kurt Weill were working in New York.

The generation of American composers who were taught by Schoenberg, Milhaud and other European emigre's is now in its prime and has prepared the way for a musical renaissance. In composition as in performance, the current generation of American musicians, at its best, has learned whatever can be taught about the art. Now, we await the genetic accident that will produce another Bach or Stravinsky, with the comfortable feeling that--with any luck--he or she will grow up in a congenial musical environment. While it is far from the ideal, American society today should be considerably more hospitable to musical genius than Vienna in the time of Mozart (who died in poverty) or Beethoven (who was a puzzlement to most fellow-citizens during his lifetime).

Classical music has enjoyed a more favorable climate here than in Latin America, where social and economic stability have been intermittent at best. But the classical roots of South American music stretch back all the way to the Renaissance. Before the landing of the Pilgrims (whose Puritan culture was not hospitable to elaborate music), Spanish and native composers in Mexico and Peru were producing polyphonic masses and motets that compare well with those of their contemporaries in Europe.

Some of this music has been performed in earlier Inter-American Festivals, with stunning effect. But the major events of both the American and the Inter-American music festivals this month are premieres--literally dozens of Washington premieres and a handful of world premieres. Tonight in the Kennedy Center, for example, we will have two world premieres: a piano concerto by German Carceres of El Salvador and the First Symphony of Thomas Ludwig of the United States. Next Saturday night, the Paul Hill Chorale will join the Festival Orchestra, conducted by Jorge Mester, in the world premiere of Brachet Para Golda Meir, a work dedicated to the late prime minister of Israel by Colombian composer Blas Emilio Atehortua. At the National Gallery, on May 23, the entire program will be devoted to the world premiere of "The White Election," a cycle of 32 songs by composer Gordon Getty with texts by Emily Dickinson.

There is a high risk factor in festivals like this. They contain a large proportion of unfamiliar music--necessarily, since most American music is still new. But for audiences, the risk is minimal; most of the festival events are free, and there is always the odd chance of being present at the birth of a masterpiece.