I'm speculating that one would have more mirror neuron activation watching a person perform live, compared to listening to a recording or watching a video. Thus the missing component that makes live performance special.

The sound feels present with live music. Speakers have this synthetic far away feel no matter how good they are.

What about live music on non-acoustic instruments so it inherently comes through a speaker?

My son isn't even a toddler so I don't think it would possibly be "mirror neurons".