Talk:Magical Mystery Cure/@comment-27578467-20170407053705/@comment-10390252-20170407082317

Several fan-writers have addressed this. The term I've seen used is 'Heart-Song'. Basically, it's a side effect of the high magical field in Equestria that is strongly associated with the qualities of Harmony. Sometimes, you've just got to sing! Everypony does it and it is generally considered to be a wonderful expression of how strong Harmony is in that pony's heart.

We humans are a bit too cynical to normally appreciate this. That is why there are several funny Equestria Girls fan-fictions in which various characters come to terms with their sudden need to burst into song when, previously, they have had no real musical inclinations at all (especially the Shadowbolts, who are still traumatised by their parts in Unleash the Magic).