Memorable photographs have this quality of openness. They don’t bring closure, necessarily, to the moment or internally, they allow viewers to bring their their own thoughts to bear.
If you substitute 'photograph' in the above quote with 'music' and 'viewers' with 'listeners', I think it's applicable. In fact, it's probably applicable to a variety of arts.
I'd been thinking how good pop music expresses a vulnerability the invites the listener to share it, but it's probably the case that good art invites an emotional response.
I wonder if allowing "viewers to bring their own thoughts to bear" is an appeal to their ego. A kind of way to make them feel like they're part of the artwork.