Terrain is as small meaningless audiovisual experiment. The infinitely scrolling landscape and the audio part are generated from the very same noise source. So what you hear is, in a way, what you see, and vice versa.
The virtually endless subtitles are generated accordingly to Raymond Queneau's Hundred Thousand Billion Poems: sonnets are cadenced by days and nights. The audio noise is filtered relatively to written vowels, as if the noise was reading the poem, because why not?