Music can be used in both a positive and a negative way, let's start from there.
by positive I mean that it creates an effect that gives a human being joy
by negative I mean that it creates an effect that creates agony on a human being.
using these statements I'm restricting my point to the effect of music on humans.
However:
There was an experiment. scientists took a plant, and put it in a room with nothing but a stereo system.
the experiment was divided to two different attempts in which they tried to effect the plant by music.
the first attempt featured classical music (I think specifically Bach)
The second attempt was some sort of metal music.
they found out that when they let the plant "hear" Bach the plant grows closer to the stereo system.
When they let it "hear" metal, it tried to grow away from the stereo system.
This is very interesting, because this proved that music has an effect on the world OUTSIDE the human psych.
if we take this into regard, and we look at some certain metal music concert and the way that the crowd often "fogo" with each other, we can definitely see that the music causes a violent effect in these humans.
Personally I believe that any sort of violence is a "bad" thing.
however, I don't believe that metal IS "bad" you can see all sorts of metal that causes good effects on humans.
So now my point is devided to two parts:
1. Music has a both positive and negative effects on humans
2. Music has a both positive and negative effects on Plants
It's pretty safe to assume at this point that music has an effect on everything.
You can experiment and scientifically explain it in many way, but the simplest way is to just watch.
music evolved everywhere in the world, so it truly has an effect EVERYWHERE.
My final point is:
Music can be used in many way, and it obviously has an actual effect on the world. it can be bad, and it can be good.
good and evil are a very delicate matter, and very, very subjective, it's truly difficult to argue the specifics of this.
It can be indeed used as a weapon, as we've seen in history
But we've also seen how it can cause great joy.
Finally, I belive, that since humans, can not exist without music, it's not up to me to decide, if it is good or "bad" it is almost (and in a way is) a force of nature, I cannot doubt the wind, or a volcano. It's just there.