John Cage thought that any sound can be music |
I don't agree. That's like saying any string of Latin characters can be English.
I think the key element a sound needs to have to be universally understood as being music is rhythm. There needs to be some sort of recognizable pattern to the sound. For example, it's not the same to have a cat walk across a piano keyboard, hitting different keys at random intervals, than to have a program generate random notes every third of a second. Neither are particularly pleasing, but at least the computer generated a pattern with the space between the notes.
Now imagine rain. While that sound can be pleasing, it's still not music because there's half a million drops hitting half a million surfaces at the same time. It's noise. Entirely different to two streams falling onto two different surfaces at regular intervals: tok-tok-tok-tak-tok-tok-tok-tak.
To answer your first question more directly, to me there are two very important aspects to vocals: being able to more or less understand when they're saying (at the very least phonetically), and matching the music. Death/black/etc. metal singing fails at both. It doesn't sound like sounds a human being would make, and it always seems to me like the singer is singing to a completely different tune. Actually, usually I can't even tell what the other tune is. Honestly, if not for the vocals I probably would like those genres, but as soon as I hear the guy start screaming I need to shut it off because the unintelligibility (boy, that was a tough one) of it ruins it for me.