The concert is over. You have just confronted the most sublime manifestation of avant-garde classical music. You survived its tone clusters and polytonality. The thundering dissonance and disharmony begin to fade away from your aural registers -- and with that, a new appreciation for sound in all its forms sets in. Out of respect for the sheer artistry of the pianist, you and the rest of your party begin to clap. The pianist, exhausted of his repertoire, walks back out onto the stage to bow to the audie--wait, what. What is he doing? Oh--Oh God. Oh God. He's come back. Oh God. He's returning to the piano.
A particularly appropriate example -- Henry Cowell's Dynamic Motion is considered a rather... out-there piece of avant-garde piano, described as an act of "pianistic violence". This alone would make a suitable BGM for any RPG final boss battle music... Then you have the Four Encores to Dynamic Motion. The fourth, Antinomy, is just asking to depict a scene where a slain alien horror resurrects itself out of its own corpse as a distorted choir sings its glory in the background.
Michael Jackson pulls this off with great effect in his music video Ghosts as the Maestro. He also does a pretty good Demon Head near the end.