John Adams refers to himself as a "post-style" composer. Franco Donatoni spoke about music having passed beyond the "school", and having entered an era of "personal style". What both gentlemen mean is that the most interesting composers no longer belong to a definable stylistic school. Certainly, different as they are (were), Donatoni and Adams both resist(ed) simple classification in their mature work.
I cannot think of myself as belonging to any discernible artistic movement. Like most composers, I suffer from the fact that most people are fairly narrow minded and, frankly, rather stupid-- they hear one work of mine and label me as something. No composer can be classified on the basis of one work. Imagine hearing only the "Liebeslieder" Waltzes and Hungarian Dances of Brahms. Imagine hearing only "Fur Elise" and "Wellington's Victory" by Beethoven. Imagine hearing only "Hungarian Rock" and "Self Portrait with Reich and Riley" by Ligeti. What label would you give these composers?
There are people who know only my lighter pieces, some of which have become very successful. My Celebration Overture is the most performed piece of orchestral music in Canada, and it is very, very light, having been written for a community orchestra. There are people who know only my first two symphonies, from performances at the Toronto Symphony, who think of me as a dangerously "modern" composer. There are people who know only my educational pieces-- it frightens me sometimes to imagine that there are professional musicians who, adjudicating festivals and exams, have never heard anything of mine other than my Prelude and Fugue for Trumpet and Piano or my Song and Dance for Violin and Piano.
In Seattle last summer, my Piano Quartet was premiered. Before the concert, the quartet and I did a presentation about the work, with excerpts. After they had played some sections, I ask the pre-concert audience present, numbering perhaps 125 people, how many people heard the music as tonal, and how many heard it as atonal. About 1/3 heard it as tonal, 1/3 heard it as atonal, and, presumably, the remaining third either didn't know or didn't care.
I don't care either. I can no longer even think in terms of "tonal" or "atonal". Music is a language that we now have free access to in every work. Each new work makes different demands on the language that we use. More importantly, composers who insist on being "tonal" or "atonal" actually reinforce the importance of the language they deny. The composers who band together like members of a motorcycle gang and insist that they and they alone are the true "school" actually make their "opposition" more important by doing so. We should no longer even think in these terms. I am constantly astonished by this old fashioned religious zeal. It is high Romanticism to imagine oneself as doing the only "true" work in music. Music must go forward, certainly, but it is impossible to force it into a specific direction. And what exactly does "going forward" actually mean? I believe that any intelligent and thoughtful artist has to agree that, to be relevant, art must be contemporary. We just disagree on what that means.
In a very real way, we are all now "post-style" composers.