Too little of Heinz-Klaus Metzger's writings or interviews have been translated into English; even — or especially — when you disagree with him, he can be a pleasure to read. Here's a taste (my hasty translation) of an interview from 2002:
"History has really shown that the emancipation of the dissonance was easier than that of women or of gays, let alone the proletariat. It really happened easily. Thus, it's no great wonder that certain revolutionary steps, in areas where they are easier to realize, get realized and even done well. Somewhere in his Aesthetic Theory, Adorno notes, entirely as an aside, that even the most ingenious architectural plan must necessarily be left behind by a simple musical composition, because, by nature, it is already limited by practical concerns that a musical composition must not face. In architecture, new structures should be built so that they do not collapse. In music, it can be good it they collapse."
"Indeed, the power of music to change the world appears to be far less than the power of the world to change music. That is the shocking recognition. The Viennese atonal revolution achieved the end of the tonal hierarchy through the atonal idiom, as this was based not only on the equality of the tones, but rather also on the equality of all conceivable relationships among them. Thus, the superstructure for a real, long overdue revolution was taken away and remains in society, to date, absent. For this reason the New Music still has no social basis and remains hanging in air."
"... that damned bourgeois age. Actually, one should have been able to go directly from Marenzio and Gesualdo into atonality. And then three hundred years of bourgeois society and culture would have had no musical superstructure. Mind you: One would have had the trans-bourgeois freedom and equality directly from the madrigalists — and therein, one must always consider Adorno's definition: Equality would be the condition in which one may be different without fear."