George Gershwin, a pioneer of the fusion of jazz, musical theater and classical idioms, wrote two essays on the significance of jazz for American music:
THE great music of the past in other countries has always been built on folk-music. This is the strongest source of musical fecundity. America is no exception among the countries. The best music being written today is music which comes from folk-sources. It is not always recognized that America has folk- music; yet it really has not only one but many different folk- musics. It is a vast land, and different sorts of folk-music have sprung up in different parts, all having validity, and all being a possible foundation for the development into art music. For, this reason, I believe that it is possible for a number of distinctive styles to develop in America, all legitimately born of folk- songs from different localities. Jazz, ragtime, Negro spirituals and blues, Southern mountain songs, country fiddling, and cowboy songs can, all be employed in the creation of American art music, and are actually used by many composers today. These composers are certain to produce something worth while if they have the innate feeling and talent to develop the rich material offered to them. There are also other composers who can be classed as legitimately American who do not make use of folk-music as a base, but who have personally, working in America, developed highly individual styles and methods. Their new-found materials should be called American, just as an invention is called American if it is made by an American.
Jazz, I regard as an American folk-music; not the only one, but a very powerful one which is probably in the blood and feeling of the American people more than any other style of folk-music. I believe that it can be made the basis of serious symphonic works of lasting value, in the hands of a composer with talent for both jazz and symphonic music.
It is difficult to determine what enduring values, aesthetically, jazz has contributed, because “jazz” is a word which has been used for at least five or six different types of music. It is really a conglomeration of many things. It has a little bit of ragtime, the blues, classicism, and spirituals. Basically, it is a matter of rhythm. After rhythm, in importance come intervals, music intervals which are peculiar to the rhythm. After all, there is nothing new in music. I maintained years ago that there is very little difference in the music of different nations. There is just that little individual touch. One country may prefer a peculiar rhythm or a note like the seventh. This it stresses, and it becomes identified with that nation. In America, this preferred rhythm is called jazz. Jazz is music; it uses the same notes that Bach used. When jazz is played in another nation, it is called American. When it is played in another country, it sounds false. Jazz is the result of the energy stored up in America. It is a very energetic kind of music, noisy, boisterous, and even vulgar. One thing is certain. Jazz has contributed an enduring value to America in the sense that it has expressed ourselves. It is an original American achievement which will endure, not as jazz perhaps, but which will leave its mark on future music in one form or another. The only kinds of music which endure are those which possess form in the universal sense and folk-music. All else dies. But unquestionably folk-songs are being written and have been written which contain enduring elements of jazz. To be sure, that is only an element; it is not the whole. An entire composition written in jazz could not live.
– George Gershwin, cited in American Composers on American Music (ed. by Henry Cowell) and Revolt in the Arts (ed. by Oliver M. Saylor ). Cited in: Nettl, Paul (1948) The Book of Musical Documents. New York: Philosophical Library, pp.346-348.