The gods must be... blind?

[Ibrîniðilpathânezel]

I tend to think that such words as sight and sound are conventions being used by the Elven authors of the story, attempting to describe perceptions of beings who are by their nature spirit, not matter. The Ainur were pure thought, and prior to Eru showing them a vision of the Music, had no concept of anything incarnate. Eru's revelation was their first exposure to physicality, and while I suspect that for them, it was an experience that went far beyond "opening their eyes" for the first time, to an Elven lore master, that would be the nearest equivalent within his own experience.