[T]he piano [in the “Quartet for the End of Time”] in particular often has “tangles” of notes thick with dissonance. Not one, but crowds of notes compete for attention under the hand of the pianist. Yet Messiaen makes of this cluster of discord something lustrous: “Tangles of rainbows.” There is something spiritual in these dissonances which makes me wonder whether the most beautiful sound might not be the most various, the most discordant. Dissonance here is not experienced as rivalry or irresolution but as an infinite and all-inclusive unity. The “harmony of heaven” might not be silence but on the contrary the capacity—and the willingness—to hear every note, to the fullness of its truth, at once. Again, there is a strong sense in which reading Schoenberg only as the creator of an authoritarian order, a musical fascist, does an injustice to his role in developing this new aesthetic. For Schoenberg, long before Messiaen, claimed to be involved in the “emancipation of dissonance” and the destruction of the old order of human certainty. In its place he founded a vast new palette of expressive possibilities on which composers such as Messiaen have been able to build with imagination and freedom. As Schoenberg wrote, “here, liberated dissonance became anew harmony, psychological chaos, a meta-sensuous order.” Releasing the potential of dissonance from the shackles of Romantic harmony is emblematic of what amounts to an ultimate pluralism.
—Desmond Manderson, Songs Without Music:
Aesthetic Dimensions of Law and Justice
(University of California Press, 2000)