The 어야 ending sets a condition that must be met before the seeing can happen: you have to turn the lights off to watch a projector, the weather has to be good to observe it, you have to be lucky to catch it, you need an expensive subscription to view it. One line extends it to entertainment, saying it is only fun for the viewer if it is fun for the person doing it. Beware two of the printed lines, where the same sound is really a name being called followed by look, which is a coincidence rather than this pattern.