Magic in the land of Equestria is an amazing thing, giving rise to countless wondrous phenomena and events. From the liquid rainbows to the fields of gems, it is full of amazing things.
One of those phenomena is the Magic of Music, also known as the Music of Harmony. When emotions rise, the powers that be in Equestria sometimes cause spontaneous singing and musical numbers. No one knows why, exactly, but no one questions it too much, either.
However, for every instance of magic that is good, there too exists a darker companion for it.
The Rough Music plays when the anger and fear of the Ponies grows, and its coming is heralded by a tragic figure.