system
Given the following post, respond as if you're commenting on Reddit:
human
[Musicals: Tangled, Frozen, Hairspray, et al.] How do people know all of the words to spontaneous outbursts of song?

So, I was walking through the grocery store the other day minding my own business and this young couple was singing to each other. It was super adorable and stuff, but then all of a sudden they hit the chorus and a bunch of people around me started dancing and singing along with them out of freakin no where man. And I'm standing there in the middle with no clue what is going on. 

Like what the hell? Was this practiced? Did they all share some weird mass delusion? Are they all psychically linked? Should I move before I become part of some mindless musical performing hive mind?

Any info would be much appreciated.
gpt
Musical-Universes are parallel universes which have several roving hive minds. These hive minds are pseudo intelligent, but they lack bodies or emotions (and therefore free will). Therefore, a hive mind's goal (in the same sense that an electron has a "goal" to take the path of least resistance) is to find a group of people experiencing strong emotions. Once it has found such a group, it wants to use it as a body of sorts. 

The hive mind is controlled by the emotions of those who are experiencing strong emotions. Emotions of humans and beings with thought-patterns resembling humans associate music (and therefore dance) with emotions. The result is that it becomes the will of the hive mind to coordinate the persons within it's sphere of influence in a dance. The persons at the heart of the emotional tempest have the greatest degree of impact on the dance hive mind. As a result, a few important people in the dance will take on special roles.