Here's what Stravinsky had to say (and we're not talking about opera here):
"I have always had a horror of listening to music with my eyes shut, with nothing for them to do. The sight of the gestures and movements of the various parts of the body producing the music is fundamentally necessary if it is to be grasped in all its fullness. All music created or composed demands some exteriorization for the perception of the listener. In other words, it must have an intermediary, an executant. That being an essential condition, without which music cannot wholly reach us, why wish to ignore it, or try to do so—why shut the eyes to this fact which is inherent in the very nature of musical art? Obviously one frequently prefers to turn away one’s eyes, or even close them, when the superfluity of the player’s gesticulations prevents the concentration of one’s faculties of hearing. But if the player’s movements are evoked solely by the exigencies of the music, and do not tend to make an impression on the listener by extramural devices, why not follow with the eye such movements as those of the drummer, the violinist or the trombonist, which facilitate one’s auditory perceptions? As a matter of fact, those who maintain that they only enjoy music to the full with their eyes shut do not hear better than when they have them open, but the absence of visual distractions enables them to abandon themselves to the reveries induced by the lullaby of its sounds, and that is really what they prefer to the music itself."
What do you think? Personally, I very much agree with Stravinsky. Although I can of course still reach the heights of ecstasy when just listening with the comfort of my earphones, I think music is rightfully seen as a physical act with a human mediator that needs to be seen.