Music has this emotional thing to it, and it touches people in crazy ways. The power of having that power is something that, once you have it, you don't want it to ever end.
You'll see a lot more blood in 'Saw' movies or something like that than you will in either of the 'Last House' movies. I kind of think it owes more to 'The Virgin Spring' which is the original source material, the Bergman movie.