>>41519367It's because of the nature of music itself. You could get all /x/ into this shit, but to put it into a nutshell, there are certain intervals of sound overall, melodic and harmonic, that just evoke an ancient almost genetic memory of forced remembrance and feeling. Certain intervals and musical patterns activate certain parts of our brain to make us feel something. And those patterns are the same objectively, but en masse, they can trigger suggestiveness in our minds, making us more receptive to certain ideas and messages.
They are common intervals and progressions, but they nevertheless have an effect on our brain that is objectively observed.
So as far as pony and EqG music goes, it's just following common trends from the 60's and even before that just works, but remixed into modern context. Sounds are objective, melodies and harmonics are semi-objective, and lyrics are subjective, but from the three aforementioned, it all flows down in terms of influencing the emotions of the mind.