So music can have negative impacts on a human being in spite of many good things it gives. :S
But is this the case? http://en.wikipedia.org/wiki/Auditory_hallucination

And if you read that part about Schumann in the link I gave, can someone clarify me how those 'angelic voices' he used to hear transmogrified into demonic voices?

Ooops. I've realized just now that this is posted in a wrong section. No wonder why there are no replies.
Sorry! Can this thread be moved to another sub-forum relevant to it?
If not possible, can someone reply please?

Music and any other art, medicine, food, etc can have positive and/or negative impacts.

Auditory hallucinations can be the result of mixed messages in the brain, damage to the brain, mis routed electrical stimuli, etc. To explain Schuman simply I suppose we can use a bad analogy of water. A fresh spritz of water on your face feels good. However, after multiple sprays over a very long period of time you would be bothered by it. The Chineese water torture uses this maddening technique.

It could also be that Schuman developed a mental illness or dementia as he aged which could easily change his perception of the voices he was hearing.

When you get down to it hearing is an interpretation of electrical signals. We know it best as the translation of sound vibrations entering the ear and being translated into nerve signals which get converted to electrical signals. The nerve sgnals get sent to the base of your brain stem, the brain stem then sends signals to the mid brain which then sends the message/signals to the temporal lobes which then send information to the auditory cortex. That's a lot of passing form one to another and if anything goes wrong then you get an incorrect message.

Also as we age our nerve groupings can cross over and mix. A good example is when we are young we have few nerve problems. Sometimes as we age we notice that when we touch a certain spot on our face we can feel it down on our ribcage somewhere. There are a mulittude or reasons and ideas why this happens - suffice it to know that it does.

Auditory hallucinations can also be generated by the mere fact that you want to hear something. Just like day dreaming you choose to visualize, in aural dreaming you choose to audioize.