Theodor W. Adorno, answered from the texts and cited to the page.
Aesthetic autonomy is the artwork's mode of social critique. The artwork is a monad that registers social antagonism in the immanent technical-historical contradiction of its material; truth content is what becomes legible in the work's failure to be reconciled, not the ideological content the work proclaims.1 Philosophy of New Music reads Schoenberg's atonality as the progressive immanent self-critique of bourgeois tonality — the second Viennese School preserves the bourgeois subject's freedom even in its catastrophe, driving the dialectic of harmonic-melodic-formal logic to the point where the established tonal language can no longer hold the historical contradictions it was constructed to contain — and Stravinsky as reactionary ritual-objectivism — the regression to pre-bourgeois rhythm-against-development, the refusal of subjective interiority that does not transcend the bourgeois subject but merely abandons it.2
The analysis is structurally aesthetic: the verdict is not a personal taste but the registration of where the music stands in the historical-technical dialectic at its moment. The late "Vers une musique informelle" (1961) shows the dialectical method working on the Darmstadt avant-garde itself, identifying where post-serial composition succumbs to its own forms of reified objectivism.34
Though artworks have scarcely ever imitated society, and their authors need know nothing whatever about it, the gestures of artworks are objective answers to objective social constellations, sometimes adapted to the need of those who consume them, more consistently in contradiction to them, but never conclusively circumscribed by this need.Philosophy of New Music, p. 102
The concept must immerse itself in the monad to the point that the social essence emerges of its own dynamic, not classify it as a special case of the macrocosm, or—as Husserl would put it—dispose of it "from on high." A philosophical analysis of the extremes of new music that takes account of its historical situation as well as of its chemism distinguishes itself in terms of its I N T R O D U C T I O N intention…Philosophy of New Music, p. 24
Rather, as the undeviating microcosm of the antagonistic constitution of man today, it breaks through those walls from within that aesthetic autonomy so carefully built up around itself.Philosophy of New Music, p. 101
What would be possible is not possible. Avant-Garde and Doctrine. The possibility of music itself has become uncertain. Not that it is endangered because it is decadent, individualistic, and asocial, as the reactionary reproach claims. It is all too little that.Philosophy of New Music, p. 88
The most-attacked specific aesthetic verdict in Adorno's corpus and the structural test case for aesthetic autonomy as a category. The post-Cage rehabilitation of Stravinsky, the post-1970s rehabilitation of minimalism, the broader shift in musicology away from the Darmstadt-Adornian modernist canon, and the cultural-studies turn against autonomy-aesthetics have all pressed the case that the Philosophy of New Music verdicts are period-bound aesthetic preferences dressed in dialectical language. Lyotard's differend reframes the question in terms that refuse the progressive-regressive dialectic itself. Defenders (Paddison, Hullot-Kentor, Goehr, Bernstein on aesthetics) press the case that the structural argument — immanent technical- historical contradiction as the bearer of truth content — is what the verdicts work out, and that the framework is what survives the specific verdicts even where particular verdicts are revised.