Post-Cagean in that in its system (which it has, in its own small way) "noise" is a term. Another interesting feature: "material" is not formless, but form-abundant (subatomic structure of the ear and eye engaged with writing). Also: there is no division between expression and concept in the system.
Questions to mull over: Why is the essay systemlike? What does this system leave out? It says that it is open to the world. Form is social. There is noise in it. Materials come from "us," our language. Etc. What is it about Mark's poetry at this time that leads him to write such an essay?